Document 6481860

Transcription

Document 6481860

Environme ntal effects
of currently used
termiticides under
Australian conditions
November 2002
Boyd, A.M., Noller, B., White, P., Gilbert, D., Smith, D., Mortimer, M., Langford, P., Martinkovic, J.,
Sadler, R., Hodge, M., Moore, M.; Murray, J., Cristaldi, C., Zalucki, M.P., Francis, I., Brown, M.,
Cruice, R., Connell, D.
National Research Centre for Environmental Toxicology
ISBN 0-9750259-0-2
EnTox 2002
This work is copyright. Apart from any use permitted under the Copyright Act 1968, no part may be
reproduced by any process without prior written permission from the authors. Requests and inquiries
concerning reproduction and rights should be addressed to Professor Barry Noller, National Research
Centre for Environmental Toxicology, PO Box 594, Archerfield, Brisbane, Queensland, 4108.
Photographs are reproduced with the permission of Amalgamated Pest Control.
To obtain further copies of this publication contact:
Professor Barry Noller
39 Kessels Road Coopers Plains (PO Box 594, Archerfield)
Brisbane, Queensland, 4108.
Tel: (+61) (07) 3274 9221 Fax: (07) 3274 9003
Email: b.noller@mailbox.uq.edu.au
Disclaimer
This document has been prepared in good faith, exercising due care and attention. However, no
representation or warranty, expressed or implied, is made as to the relevance, accuracy, completeness or
fitness for purpose of this document in respect of any particular users circumstances. Users of this
document should satisfy themselves concerning application to and, where necess ary, seek expert advice
about their situation.
The National Research Centre for Environmental Toxicology (EnTox), Energex Limited, the Department
of Public Works, Queensland, the Department of Housing, Queensland, Gold Coast Water, the Queensland
Environmental Protection Agency, Queensland Rail, Brisbane City Council, Queensland Health Scientifi c
Services, Ergon Energy, The University of Queensland, FMC Chemicals Pty Ltd and Griffith University
shall not be liable to any person or entity with respect to any liability, loss or damage caused or alleged to
have been caused directly or indirectly by this publication.
This document does not necessarily represent the views of the National Research Centre for Environment al
Toxicology, Energex Limited, the Department of Public Works, Queensland, the Department of Housing,
Queensland, Gold Coast Water, the Queensland Environmental Protection Agency, Queensland Rail,
Brisbane City Council, Queensland Health Scientifi c Services, Ergon Energy, The University of
Queensland, FMC Chemicals Pty Ltd, or Griffith University
Designed by: Chris Clayton
Printed by: University of Queensland Printery.
List of contributors
Ms Ann-M arie Boyd
Dr M ichael Brown
FM C Chemicals Pty Ltd and Griffith University
Professor Des Connell
Griffith University
M r Carmelo Cristaldi
Ergon Energy
M r Roland Cruice
Department of Housing, Queensland
M r Ian Francis
FM C Chemicals Pty Ltd
M r Dale Gilbert
Department of Public Works, Queensland
Dr M ary Hodge
Queensland Health Scientific Services
M r Peter Langford
Queensland Rail
M r John M artinkovic
Brisbane City Council
Professor M ichael M oore
Dr M unro M ortimer
Environmental Protection Agency
M r Jasen M urray
Ergon Energy
Professor Barry Noller
Dr Ross Sadler
M r David Smith
Gold Coast Water
M r Peter White
Energex Limited
Professor Myron Zalucki
The University of Queensland
a
b
c
Termite entry points crossing exposed slab edges (a and b) and entering through weepholes (c).
Photos courtesy of Amalgamated Pest Control.
Termite caps can stop termites entering structures, to a certain degree. In this case the cap was
nailed to the stump top during construction, allowing termites to enter the building through the
nailhole after the nail had rusted away. Photos courtesy of Amalgamated Pest Control.
Examples of termite damage. Photos courtesy of Amalgamated Pest Control.
Contents
List of Figures
List of Tables
Objectives
Audience
Key words
Abbreviations
Definition of terms
Acknowledgments
ii
ii
iii
iii
iv
iv
v
vii
Executive summary
Preamble
1
3
1. Introduction
4
2. Termite ecology
5
3. Historical termite management in Australia
7
4. Current chemical termite management in Australia
4.1 The organophosphate termiticides
4.2 The natural pyrethrin and synthetic pyrethroid termiticides
4.3 The chloronicotinyls
4.4 The phenyl pyrazoles
4.5 Growth inhibitors
4.6 Other chemicals
7
10
11
14
16
17
17
5. Migration and behaviour of currently used termiticides in soils
18
6. The efficacy and persistence of currently used termiticides in soils
19
7. S olvents
19
8. Toxicology and risks to human health from termiticide usage
20
9. Potential effects of termiticides on non-target species
23
10. Incidents involving termiticides in southeast Queensland
25
11. Potential new chemical treatments
26
12. Biological control
26
13. Alternative treatments and management tools
27
14. Future directions
Recommended further reading
References cited
Index
31
34
37
44
i
List of Figures
Figure 1. Key changes in termite management practices in Australia
8
Figure 2. Generalised fate of termiticides after application to soil
9
List of Tables
Table 1. Summary of the physicochemical properties of chlorpyrifos
10
Table 2. Summary of the physicochemical properties of permethrin
11
Table 3. Summary of the physicochemical properties of bifenthrin
12
Table 4. Summary of the physicochemical properties of alpha-cypermethrin
13
Table 5. Summary of the physicochemical properties of deltamethrin
14
Table 6. Summary of the physicochemical properties of imidacloprid
15
Table 7. Summary of the physicochemical properties of fipronil
16
ii
Objectives
This document presents a review of historical, current and future uses of termiticides in
Australia. It broadly examines the migration and fate of currently used termiticides in soils. The
focus is on identifying risks to the environment and human health and identifying knowledge
gaps, research priorities and industry concerns. Where detailed information or reviews are
available elsewhere, either electronically or in print, users are directed to those.
Audience
This document is primarily intended for use by environmental health agencies reviewing risk
assessments, by people preparing risk assessments for environmental health agencies and by
those regulatory agencies reviewing risk assessments. It is also intended to be of assistance to a
broader audience seeking information about termiticides in Australia.
iii
Key words
termite, termiticide, organochlorine, organophosphate, chlorpyrifos, permethrin, cypermethrin,
bifenthrin, imidacloprid, fipronil
Abbre viations
AchE – Acetylcholinesterase
ADI – Acceptable Daily Intake
AEPM A – Australian Environmental Pest M anagers Association
ARD – Acute Reference Dose
AS – Australian Standards
ATPase/ATPASE - Adenosine Triphosphatase
BCA – Building Code of Australia
BERU – Built Environment Research Unit, Queensland Department of Housing
EC - Emulsifiable concentrate/s
EPA – Environmental Protection Association (USA)
EPA (Aust.) – Environmental Protection Association (Australia)
FSANZ – Food Standards Australia and New Zealand
GUS – Groundwater Ubiquity Score GUS = log10(half-life) x (4 – log(Koc ))
Hg - M ercury
IARC – International Agency for Research on Cancer
kg – kilograms
Koc – Soil sorption constant
Kow – Water octanol partition coefficient
L – litre
LC50 – the concentration (in water, food or air) that results in 50% mortality
LD50 – the dose that results in 50% mortality
mg/kg – milligrams per kilogram
mg/L – milligrams per litre
M SDS - M aterial Safety Data Sheets
NHM RC – National Health and M edical Research Council (Australia)
NOEC – No Observed Effect Concentration
NOEL – No Observed Effect Level
NRA – National Registration Authority for Agricultural and Veterinary Chemicals (Australia)
ppm – parts per million
TCP - 3,5,6-trichloro-2-pyridinol
TGA – Therapeutic Goods Act (Australia)
iv
Definition of terms
Terms and parameters are used to describe the physical, chemical and toxicological properties
of a pesticide. Described below are some of the terms used in this report to summarise the
characteristics of the termiticides listed.
Persistence describes the tendency of a chemical to survive in the environment without
transformation or loss. Persistence in soils is usually described by the half-life (the time taken
for the chemical to degrade to half of the original concentration). Degradation of a pesticide
may be by routes, including microbial degradation (breakdown by microorganisms), chemical
degradation (breakdown due to reactions with air, water and oxygen, or other chemicals), and
photodegradation (breakdown of pesticides by sunlight). The half-life may be established under
different conditions, varying pH or soil type or in matrices other than soil (i.e. in water). The
resultant values can therefore cover a large range and may only be of use as a comparative or
relative description, and can vary greatly due to differences in soils, biota, climate and other
factors. For this reason, soil half-life values should be interpreted with caution. Generally:
•
•
•
Termiticides described as “persistent” have half-lives of >100 days
Termiticides described as “moderately persistent” have half-lives of 30–100 days
Termiticides described as “non-persistent” termiticides have half-lives of <30 days
The mobility of a pesticide in soil, air and water is influenced by its persistence and can be
defined by parameters, including sorption, water solubility and vapour pressure.
S orption is the attraction between a chemical and soil, vegetation, or other surfaces, but often
simply refers to the binding of a chemical to soil particles. The sorption constant Koc
describes the potential to bind to soil particles, based on organic carbon content. Put simply, the
higher the Koc value, the greater the sorption. Differences in termiticide formulations and soil
types can influence sorption.
Pesticides may also volatilise, with rates determined by the moisture content of the soil, and the
pesticide’s vapour pressure, sorption and water solubility. Volatilisation from moist soil is
described by the Henry’s Law Constant, calculated by the ratio of the vapour pressure of the
chemical to its solubility in water, which characterises the tendency for a pesticide to move
between the air and the soil water. The higher the Henry's law constant, the more likely it is
that a pesticide will volatilise. Vapour pressure is the tendency of a chemical to volatilise – a
-8
termiticide with a vapour pressure of less than 1.0 x 10 mm Hg has a low tendency to
-3
volatilise, while those with vapour pressures of more than 1.0 x 10 mm H g have a high
tendency to volatilise. S olubility in water describes how much of a chemical will dissolve in
water, usually measured at 20oC or 25oC. Termiticides with high solubility are more likely to
be mobile in the soil, they are likely to leach to groundwater and be involved in runoff.
The Groundwater Ubiquity S core (GUS is a value derived from persistence (half-life) and
sorption (Koc ). It is used to rank the potential for chemicals to leach and move into
groundwater. It is calculated from the formula GUS = log10 (half-life) x [4 – log (Koc )].
Termiticides with a GUS of less than 0.1 are extremely unlikely to move toward groundwater,
whereas those with a GUS of more than 4 have a very high tendency to leach and move
towards groundwater. Pesticide movement ratings are derived from the GUS: values of 1.0 to
2.0 are low, 2.0 to 3.0 are moderate, 3.0 to 4.0 high, and values greater than 4.0 are very high.
v
Bioaccumulation, the capacity of a chemical to be stored in fatty tissue from environmental
uptake depends on animal metabolism and the Octanol water coefficient (Log Kow) of the
chemical in question. Log Kow is the Octanol water partition coefficient, which describes the
ability of a chemical to partition between an aqueous and a lipid phase. It is a measure of a
chemical’s potential for bioconcentration. A Log Kow value of greater than 3 indicates a
propensity for a chemical to bioaccumulate in fat.
Toxicity refers to how poisonous a pesticide is. Acute toxicity describes effects that appear
within 24 hours after short-term exposure. Acute toxicity measures are used to compare
different pesticides. Acute toxicity is usually measured by the response of test animals to oral,
dermal and/or inhalation exposures. Chronic toxicity results in delayed effects, after continual
or repeated exposure over a long period of time. The effects measured for pesticides are
reproducti ve effects (effects on reproductive systems or reproductive ability); teratogenic
effects (effects on unborn offspring); carcinogenic effects (producing cancer); oncogenic
effects (causing tumours); mutagenic effects (permanent effects on inheritable genetic
material); neurotoxic effects (effects on the nervous system) and immunosuppression
(suppression of the immune system).
Toxicity levels are derived from animal studies (usually rats or mice) and therefore may or may
not be directly applicable to humans. The LD50 doses are usually expressed as the amount in
milligrams of pure active ingredient per kilogram (kg) body weight of test animals. The lower
the LD50, the more toxic the chemical is. Pesticides are packaged with “signal words”
depending on how toxic they are. They are labelled “Danger–Poison”, “Warning” or
“Caution” accordingly and grouped from slightly toxic to highly toxic as described below:
•
Highly toxic – “Danger–Poison”, Oral LD50 mg/kg <50; dermal LD50 mg/kg <200;
inhalation LC50 mg/L <0.2
•
Moderately toxic – “Warning”, Oral LD50 mg/kg 50–500; dermal LD50 mg/kg 200–
2000; inhalation LC50 mg/L 0.2–2
•
Slightly toxic – “Warning”, Oral LD50 mg/kg 500–5000; dermal LD50 mg/kg 2000–
20,000; inhalation LC50 mg/L 2.0–20
•
Slightly toxic – “Warning”, Oral LD50 mg/kg >5000; dermal LD50 mg/kg >20,000;
inhalation LC50 mg/L >20
vi
Acknowledgments
The authors thank the following people for their assistance and advice in the preparation of this
report.
John Cheadle (retired, formerly of Arrest-a-Pest), John Field (AEPM A, formerly of
Amalgamated Pest Control), Shaun Hale (Amalgamated Pest Control), M ichael Ball and Bill
Wiersma (Department of Public Works and Housing, Queensland), Peter Dobson (Brisbane
City Council), Ben Foster (Dow Agrosciences), Brenton Peters and John Fitzgerald
(Queensland Department of Primary Industries – Forestry Division), John French (University
of the Sunshine Coast), John M ott (University of Queensland), Ian M arshall and Steven Begg
(Queensland Health).
vii
Executive summary
In response to the emerging huge cost to buildings and other wooden structures of termite
damage, and concerns about the environmental and public health consequences of the large
quantity and frequent reapplication of termiticides as a result, government and industry
research personnel, pesticide suppliers and applicators from organisations in Queensland has
identified a need to have appropriate information, reflecting local conditions, on the
environmental and health effects of the currently used chemicals for the treatment of termites.
Current literature was reviewed on the subject of environmental effects of termiticides together
with a review of previous, current and future uses of termiticides in the context of appropriate
techniques for termite control and treatment priorities.
Currently in Australia, we may be enjoying a period of overlap where older buildings are still
being protected by the organochlorines while new structures are treated with organophosphates.
Houses built before 1985 may still be protected to some extent by the organochlorine
termiticides applied to them. However, the effectiveness of the residual organochlorines will
have been reducing over time, and older houses may be at risk of termite infestation. The
potential costs of re-treatment and repairs are likely to increase dramatically in the future as
older slab-on-ground dwellings become susceptible due to the eventual failure of the
organochlorine termiticides.
The phasing out of organochlorine termiticides in Australia was undertaken to minimise impact
to the environment and, to a lesser extent, public health. It was seen to be a positive step to
replace long-persistent chemicals as barriers to termites with those having high activity but a
shortened persistence in soil. The transition from 1995 when the organochlorine termiticides
were phased out has led to the realisation that significant information gaps and limitations have
arisen from the application of replacement chemicals as termite barriers.
Information on the migration of currently used termiticides through the soil has been examined,
where available, and found to be closely related to soil type. There is limited publicly
accessible information, and specific studies are warranted to investigate the behaviour and
environmental fate of termiticides under Australian soils and environmental conditions.
A review of information on termite behaviour shows that more information is required to
understand the foraging activity of Australian termites.
Several requirements are apparent:
•
M ore information is required on Australian termite biology, taxonomy, ecology and
behaviour.
•
The problem of termite infestation needs to be defined, locally and nationally, and highrisk structures and building types identified so that preventive measures can be taken in
terms of design and construction.
•
Further education is required for homeowners, builders, designers, legislators and
landscape designers so that they can reduce the risk of infestation through the avoidance
of practices in landscaping and design that inadvertently favour termites.
1
•
There needs to be a specific focus on the creation of alternative barriers, that takes into
account the limitations of currently available physical barriers. An innovative approach to
barrier design is needed that incorporates the specific features of slow-release chemicals
that are more acceptable to the environment and public health.
•
Best practice guidelines for minimising the environmental and public health effects of
termite control applications need to be developed.
2
Preamble
There are huge costs associated with the prevention and treatment of termite infestation in
wooden structures and reapplication of chemical barriers is required every 2 to 10 years
depending on the products used and local conditions. Following reports in the Australian press
of fraudulent operators, and subsequent failure of termiticide treatments, coupled with poor
building practices, public confidence in the termite management industry has waned. In
addition, there have been incidences of contamination of potable water with solvents following
treatment of existing buildings with termiticides, and reports of fish kills as a result of
pesticides contaminating waterways. There are also concerns about the environmental and
public health consequences about the application and reapplication of large quantities of toxic
chemicals over time. For example, in the USA, there has been a partial ban on the use of
chlorpyrifos since 2000, with most home and outdoor use of the chemical stopped, and a total
phase-out planned. The ban is a result of public concern about pesticide exposure in children
following the detection of developmental effects in rats. This document addresses the concerns
of individual stakeholders and the public by providing a single reference pertaining to termite
management options available in Australia. The purpose of this report is to collate available
information of importance to as wide a representation of stakeholders as possible, and to
examine whole-of-ecosystem issues.
Recognising gaps in knowledge of each component of termite management, from termite
ecology through to present and future uses of termiticides in the context of appropriate
techniques, is critical in terms of identifying information for acceptable industry practice for
termite management and public concerns. This report identifies such knowledge gaps in terms
of industry, public and client priorities and provides a basis for planning to address those needs.
This report seeks to provide a review on aspects of environmental effects of currently used
termiticides, along with a review of previous, current and future termiticides in the context of
appropriate techniques for termite management and client priorities. The report provides a basis
for developing best practice guidelines.
3
1. Introduction
Termites consume wood and cellulose and serve an important ecological function by
converting dead trees into organic matter. Unfortunately, the wood in buildings and other
structures such as wooden power poles and bridges is equally appealing to termites and
infestation can cause considerable damage. On a local level, the Queensland Department of
Housing spent $410,000 managing termite infestations in public housing during the 1999–2000
financial year. In the Ipswich, Woodridge and Capalaba areas in southeast Queensland the
estimated cost of repairs for termite damage ranged from $18,000 to $60,000 per property
(Department of Public Works’ Built Environment Research Unit figures, January 2000). On
average, termite infestations cost approximately $1500 in treatment, and repairs of $5000 for
each building affected (Caulfield, 2002). It is estimated that 10% of Australian houses have had
or will have termite infestations, with that figure rising to 65% in some areas – a resulting per
annum cost of $4 billion (Caulfield, 2002). M anagement of termites, and eradication of exotic
species is also costly – a campaign to eradicate drywood termite Cryptotermes brevis (Walker)
in Queensland is estimated to have cost $4.2 million by 1998 (Peters and Fitzgerald, 1998).
Worldwide, damage caused by termites is estimated at U.S $22 billion per annum in terms of
damage to wooden structures (La Fage et al., 1988). Treatment and prevention of termite
damage is therefore needed, and may give rise to unwanted side effects.
Until 1995, effective chlorinated hydrocarbon (organochlorine) termiticide treatments were
used to create barriers to termites in Australia. These have since been replaced with other, less
persistent, chemicals and physical barriers. As a consequence, chemical termiticides need to be
reapplied on a regular basis, averaging every 3 to 5 years depending on local conditions. There
is a relative lack of knowledge of the consequences of repeatedly using these replacement
chemicals under Australian conditions. Currently, chlorpyrifos (Dow Agricultural Products)
and bifenthrin (FM C Chemicals Pty Ltd) are the termiticides in most common usage in
Australia, with varying formulations of chlorpyrifos, permethrin, alpha-cypermethrin,
bifenthrin, imidacloprid and fipronil registered for use in Australia by the National Registration
Authority (NRA). With the withdrawal of chlorpyrifos from use in applications in the US, the
use of chlorpyrifos in Australia has also reduced, with a corresponding increase in bifenthrin
and imidacloprid use.
The major use of termiticides in Australia is for preventative treatments applied to buildings
before and during construction, and to existing structural features such as timber power poles
and bridges. Treatments of infestations in existing buildings, preventative and remedial
applications to wooden power poles and other wooden structures such as timber trestles and
bridges are also significant.
4
2. Termite ecology
Australia’s termite fauna is diverse, represented by five families (M astotermitidae,
Termopsidae, Kalotermitidae, Rhinotermitidae and Termitidae). Within these families there are
40 known genera and more than 266 described species. Termites may be grouped as
dampwood, drywood or subterranean, depending on their habits. As suggested by the name,
dampwood termites live in rotten wood, particularly in logs or in damp sections of trees.
Although they sometimes inhabit rotten wood in structures they are not considered to be of
economic concern. The drywood termites have no contact with the ground, and obtain their
moisture requirements from the wood in which they live. Drywood termites are considered of
economic importance, with the exotic West Indian drywood termite Cryptotermes brevis
Shiraki identified as the most destructive species (Peters and Fitzgerald, 1998). Subterranean
termites are those that require contact with the ground or moisture and they are responsible for
damage to timber structures in buildings and in trees. Termites play a key role in the nutrient
cycles of tropical ecosystems. Whitford (1991) recorded long-term negative effects on soils,
vegetation and organic material following removal of termites from desert rangelands in New
M exico, USA. Soils without termites had lower infiltration and water content and higher
nitrogen levels. The changes in soil characteristics resulted in different plant species
composition and vegetation productivity.
In Australia, the majority of pest termites are native (the exception is C. brevis), which means
they are well adapted to local conditions and may be quite resistant to treatments when
compared to situations in the USA where the major pest species, Coptotermes formosanus
Shiraki, are exotic and restricted in range and habitat and therefore potentially easier to control.
In addition, the majority of baseline studies conducted into the effectiveness of chemical
treatments have been conducted in North America on C. formosanus and therefore may not be
directly transferable to Australian conditions and species. Of the termites that exist in Australia,
relatively few are considered to be pests of sound timber, with the most economically
important being C.acinaciformis (Froggatt), C.acinaciformis raffrayi Wasmann, C. michaelseni
Silvestri, Mastotermes darwiniensis (Froggatt), Nasutitermes exitiosus (Hill) and
Schedorhinotermes reticulatus (Froggatt).
Subterranean termites forage for food by means of covered runways (galleries), which extend
from the central nest to food sources above or below ground. They communicate by secreting
pheromones. Colonies consist of distinct castes, each performing a specialised task within the
colony. Workers provide food for the colony, feed the other caste members and excavate
galleries, while soldier termites defend the colony and tend to be equipped with mandibles or a
proboscis (depending on the species) for defence. Reproductives are winged, and tend to
swarm after summer rains to establish new colonies. On returning to the ground the
reproductives shed their wings and search for food and moisture in the soil. After digging a
chamber near a food source, the pair mate and a colony is begun. Supplemental reproductives
can be formed in some species within 3 to 4 months after separation from the founding colony
(Pawson and Gold, 1996), making it important not to fractionate the colony during
management procedures.
5
The management of social insects differs from that of other pests. The complex social
interactions of termites (grooming, chemical communication, caste differentiation) should be
taken into account, and can be exploited when treating colonies. For example, worker castes
gather food and return it to the colony, therefore by providing poison baits or dusting workers
with a slow acting toxin, termiticides can be transported to, and spread within, the nest.
Grooming behaviours by termites within the nest can result in the toxic dusts that coat
returning workers, being spread quickly to other colony members.
There is some evidence that social interactions help termite colonies to overcome physiological
stresses such as starvation and disease, and possibly the effects of poisons. For example,
Ledoux et al. (2001) exposed Cornitermes cumulans (Kollar) workers to chlorpyrifos in order
to evaluate any effects of group size on tolerance to poisoning. Survival of poisoned and
control termite groups depended on the numbers of individuals in the group. The significance
of this is that there is some “socially-induced” ability to overcome physiological stress. Social
functions may enhance mechanisms that can help in the detoxification of termites exposed to
poisons. The mechanisms by which this occurs are not understood and require further
investigation. There is much variation in the breeding strategies of termite species, which in
turn may influence the effectiveness of chemical treatments.
Tunnelling behaviours of termites through soil treated with pesticides need to be understood,
and the ability of a termite colony to tunnel through pesticide-treated soil may be affected by
population density. For example, Jones (1990) found that C. formosanus at high population
levels were able to construct more and longer tunnels and therefore potentially able to cross
termiticidal barriers. Other factors influence tunnelling, e.g. studies of C. formosanus indicate
that the size, length and complexity of search tunnels excavated by termites is dependent upon
available food sources (Hedlund and Henderson, 1999). When food size (the amount of food
available in the feeding chamber) is large, feeding activity and survival are increased, but
search tunnel volume is reduced. Termite foraging activity appears to be influenced by seasonal
variation in temperature. Evans and Gleeson (2001) found that C.lacteus in artificial feeding
stations foraged further from their mounds in summer, whereas in winter they were more likely
to be found clustered close to the mounds. Variations in foraging activity also occurred
according to air and soil temperature changes, demonstrating that seasonal and daily changes
influence activity and foraging behaviour. This indicates that, for these species at least, termites
adjust search activity in response to available food supply and environmental conditions. An
understanding of these behaviours may be of use for increasing the efficacy of baiting for
termite management. At present bait and monitoring systems rely on termites finding and
feeding on the baits provided, in a hit or miss fashion.
6
3. Historical termite management in Australia
In Australia prior to 1962 arsenic dusting was the most common means of small-scale termite
management. Nests were located and dusted directly with arsenic trioxide powder. Before
1995, subterranean termite management in Australia was based on the use of highly persistent
organochlorine insecticides (Peters and Fitzgerald, 1998), such as aldrin, dieldrin, chlordane
and heptachlor (known collectively as cyclodienes, because of their particular chemical
structure), which were well suited to slab-on-ground housing construction. Because of their
chemical stability, they were extremely effective Australia-wide, and had no immediate
adverse health effects at the levels of exposure arising from the approved use. Due to
increasing environmental and public health concerns (primarily with their persistence in the
environment and their tendency to accumulate in the fat of animals and humans), these
chemicals were voluntarily withdrawn from the market in 1995 (Figure 1) and alternative
strategies for termite management have been developed.
Organochlorines came into common usage after 1962, and provided long-term protection
against termites. Organochlorines used under slabs offered protection from termites for up to
30 years, and pre-treated wood for up to 10 years. For some species organochlorine baits
(M irex) were used with success e.g. M irex packed into baits with Eucalyptus regnans and agar
gel was effectively used against M. darwiniensis in the Northern Territory (John Cheadle, pers
com.). The Northern Territory and Western Australia received an extension to its use of
organochlorines in the form of M irex and M irant baits for M. darwiniensis management only,
currently registered until June 2003. These products are largely used for prevention of termite
infestation of fruit trees in orchards. M ethyl bromide gas is still used to fumigate buildings,
timber and furniture for drywood termites, such as C. brevis.
Organophosphates and pyrethroids have since been offered as alternatives to the
organochlorines, however they are effective against termites for a much shorter time, due to the
shorter lifetimes of these chemicals which break down relatively quickly and therefore do not
provide long-term protection. The need for more regular applications of the newer, lesspersistent chemicals results in an increased chance that householders and the pest control
operators will be more frequently exposed to the chemicals.
4. Current chemical termite management in Australia
The withdrawal of the organochlorines as termiticides in Australia has by necessity encouraged
the introduction and investigation of new products and methods for termite management.
Previously, because the organochlorines were so effective, there was apparently little
commercial incentive to develop new chemicals or barrier controls. Chemical control can be
divided broadly into preventative and curative. New buildings are treated with a chemical
barrier beneath and surrounding their slabs. Where access to slabs is not practical for underslab termiticide application, reticulation systems can be installed pre-construction, enabling
repeated application of termiticides over time. Where a termite infestation has occurred,
chemicals may be applied as spot treatments, sprays, baits or gases. There are termiticides
registered for use in Australia as varying formulations of synthetic pyrethroids (e.g. permethrin
and bifenthrin), organophosphates (chlorpyrifos), the chloronicotinyls (imidacloprid), arsenic
trioxide (as a dust for spot treatments), and recently a phenyl pyrazole (fipronil), along with
wood preservatives such as boron, copper, fluorine and creosote that are also used alone or in
combination to prevent termite attack.
7
2002
•
2001
•
•
2000
•
•
1995
•
•
•
1993
•
1990
•
1988
•
1987
•
1986
•
Fipronil registered for use as a termiticide
in October.
AS 3660.1 added to BCA, specifies procedures
for chemical soil barriers.
January 2001, the Queensland provisions of
BCA amended to address installation of
termite management systems in houses and
buildings to incorporate durability of termite
management systems in new buildings.
AS 3660 parts 2 (existing buildings) and 3
(termite management systems assessment)
are added to BCA.
Queensland government reviews and
tightens regulations.
Organochlorine. Withdrawn from use
AS 3660.1 incorporates new barrier
systems.
NRA approves chlorpyrifos and bifenthrin
for use under slabs during construction.
Federal government inquiry into the use of
organochlorines in Australia.
NHM RC review of organochlorines as
termiticides.
Organochlorines under increasing
international pressure from environmental,
health and union groups.
Organochlorines withdrawn from
agricultural use.
Draft BCA legislation considers structural
components only.
< 1986
• Building regulations apply to “whole-ofhouse”.
Figure 1. Key changes in termite management practices in Australia.
8
Repairs for termite damage potentially up to
$18,000 to $60,000 per property (Qld. Dept. Housing
figures). Average figures are approximately $1500 in
treatment, with repair costs of $5000 per building
(Caulfield, 2002).
An estimated 10% of Australian houses have had or will
have termite infestations, with that figure rising to 65% in
some areas, with a resulting per annum cost of $4 billion
(Caulfield, 2002).
M ovement of
volatiles
into the air and
photodegradation
Original application
UV degradation in exposed areas
Possible
uptake
by animals
Possible plant
uptake
Possible
runoff
Vertical
movement into
soil and
groundwater
Degradation –
chemical
Leaching
Figure 2. Generalised possible fate of termiticides after application to soil.
Clipart sourced from http://www.free-clipart.net
9
4.1 The organophosphate termiticides
Chlorpyrifos (Dow Agricultural Products) – Trade names internationally include Pyrinex,
Brodan, Detmol UA, Dowco 179, Dursban, Empire, Eradex, Snare, Lorsban, Paqeant, Piridane,
Scout, Deter and Stipend. Chlorpyrifos is a widely used organophosphate insecticide, which is
active against insect pests. The toxicity of chlorpyrifos results from the action of the metabolite
chlorpyrifos oxon, which inactivates acetylcholinesterase (AchE) at neural junctions. Overstimulation of the peripheral nervous system then results in death. Chlorpyrifos acts on insects
primarily as a contact poison, and has some action as a stomach poison. The solvents used in
formulations are usually hexane or xylene. The environmental fate of chlorpyrifos, including
comprehensive solubility, sorption and degradation data, has been extensively reviewed by
Racke (1993).
Chlorpyrifos
[CAS 2921-88-2]
C 9 H11 Cl3 NO3 PS
0,0-diethyl 0-(3,5,6-trichloro-2pyridyl)
phosphorothioate.
Property
Group
Physical state (at 25o C)
Melting point
Vapour pressure
(mm Hg at 25o C)
Solubility in water (mg/L)
Value
Organophosphorothiote compound
Solid
41.5–43.5o C
2 x 10-5
Source
EXTOXNET
20.4
Average sorption coefficient (Koc)
Log Kow
Metabolites
8498
4.7 – 5.3
TCP 3,5,6-trichloro-2-pyridinol in rats and
humans; TMP -3,5,6-trichloro-2ethoxypyridinein in soil CPF-oxon
OSU Ext. Pesticide
Properties Databas e
Racke 1993
EXTOXNET
EXTOXNET
Half-life
(under different conditions)
•
•
•
Pesticide movement rating
•
•
•
Very
11– 141 days in 7 soils
loamy sand to clay, soil pHs from 5.4
– 7.4
16 – 72 days in distilled water (pH 5
– 9)
irrigated loam 69 – 90 days
non-irrigated loam 48 days
62 hours in humans
low
Racke et al. 1992
Racke et al. 1993
Pike and Getzin 1981
Pike and Getzin 1981
EXTOXNET
OSU Ext. Pesticide
Table 1. Summary of the physicochemical properties of chlorpyrifos
Chlorpyrifos has low solubility in water and partitions readily from aqueous to organic phases
(Racke, 1993). Because it is tightly adsorbed by soil, it is not expected to leach significantly
and movement through soil is limited. Volatilisation from the soil surface due to its
intermediate vapour pressure can contribute to loss. Cleavage of the phosphorothioate ester
bond to form 3,5,6-trichloro-2pyridinol (TCP) is the major path to degradation. Once this
occurs TCP is degraded by photolysis. The vapour phase of chlorpyrifos can be destroyed by
hydroxyl radicals. Alternatively, it may be adsorbed by airborne particles, and may be
reactivated and taken up by local biota. High soil temperature, low organic content and low
acidity increase the degradation of chlorpyrifos.
10
Chlorpyrifos has a half-life soils ranging from 2 weeks to over 1 year, depending on the soil
type, climate, and other conditions. As documented by Racke et al. (1993), depletion rates for
chlorpyrifos in soil increase with temperature, with each 10oC rise in temperature
approximately doubling the depletion rate (M urray et al., 2001). Chlorpyrifos dissipates more
rapidly from water than from soil, with half-lives of 16 to 72 days in distilled water (pH 5 to 9)
(Racke 1993). Volatilisation is the primary route of loss of chlorpyrifos from water. However,
it partitions from the water column to sediments, and as a result desorption from sediments can
cause long-term residual contamination of the water column.
4.2 The natural pyrethrin and synthetic pyrethroid termiticides
Pyrethrins are natural insecticides derived from the flowers of certain species of
Chrysanthemum plants. The plant extract (pyrethrum) contains pyrethrins (pyrethrin I and II).
Pyrethroids are synthetic analogues of pyrethrins. They are used to form chemical barriers to
repel and/or kill termites and are used in the control of many insect pests. Pyrethroids act by
inhibiting the nervous system of insects inhibiting ATPase enzyme production, and affecting
sodium ion channels, and in some cases affecting GABA (gamma-aminobutyric acid) action.
Permethrin
[CAS 52645531]
C 21 H20 Cl2 O3
3-(2,2-dichlorethenyl )-2,2-dimethyl-, (3phenoxyphenyl) methyl ester
Property
Group
Value
Synthetic pyrethroid
Pale brown liquid or crystalline colourless
Melting point
Vapour pressure
(mm Hg at 25o C)
34 – 35o C
0.045
Average sorption coefficient
(Koc)
Log Kow
100,000
Half-life
Figure: Ware 1999
Source
EXTOXNET
0.2
6.1004
•
< 2.5 days in near-estuarine water
exposed to sunlight
• 4.6 days in soil 30 to 38 days
Extremely low
OSU Ext. Pesticide
Table 2. Summary of the physicochemical properties of permethrin
Permethrin is the active ingredient in broad-spectrum insecticides, including termiticides. In
most cases permethrin (25:75 CIS:TRANS) is present at 500 g/L and mixed with hydrocarbon
solvents. Example products internationally include Dragnet (FM C (Chemicals) Pty Ltd),
Perigen 500 (Bayer Cropscience Pty Ltd) Imperator (Syngenta Crop Protection Pty Ltd) and
Pestgard (Ecolab Pty Ltd). Permethrin is currently available in Australia as a dust, or liquid
used to treat active infestations. Elsewhere, it is also used in wood preservatives to prevent
11
termite attack, for example in Rurply industrial plywood protectant (Bayer Cropscience Pty
Ltd) the active ingredient is permethrin combined with benzalkonium chloride.
Bifenthrin (FMC Chemicals Pty Ltd) – Trade names internationally include Biflex, Talstar,
Bifenthrine and Brigade. Bifenthrin (Biflex) is used in Australia as a barrier termiticide as well
as for treatment of active infestations. Bifenthrin (Bistar) is also used as a wood preservative in
Australia. As with other pyrethroids, bifenthrin is an insecticide and acaricide, which causes
paralysis in insects by affecting the nervous system.
Property
Group
(2-methyl-1, 1-biphenyl-3-y1)-m ethyl-3- (2chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethyl
cyclopropanecarboxylat e or (2-methylbiphenyl3-ylmethyl (Z)-(1RS, 3RS)-3-(2-chloro-3,3,3trifluoroprop-1-enyl)-2,2dimethylcyclopropanecarboxylate.
Value
Light brown viscous oil
Melting point
57 - 64oC
Vapour pressure
(mm Hg at 25o C)
Solubility in water at 25o C (mg/L)
1.8x10-7
Average sorption coefficient (Koc)
1,000,000
131,000 to 302,000
>6
Bifenthrin
[CAS 82657-04-03]
C 23 H22 ClF3 O2
Octanol-water coefficient (Log
Kow)
Metabolites
Half-life
Source
EXTOXNET
0.01
•
In soil: 2-methyl-3-phenyl-benzyl
alcohol, 2-methyl-3-phenylbenzoi c
acid, 2-methyl-3-phenylbenzaldehyde,
4-hydroxy bifenthrin, and cis, trans-4(2-chloro-3, 3,3-trifluoro-1-propenyl)3,3-dimethylcyclopropanecarboxylic
acid
• By photolysis: 4’hydroxyl bifenthrin
• Anaerobi c 97 – 156 days
• Aerobic 65 – 125 days
• 7 days – 8 months in soil
• 65 – 125 days in soil
• Photodegradation >100 days
Extremely low
OSU Ext. Pesticide
Table 3. Summary of the physicochemical properties of bifenthrin
The Koc values of bifenthrin indicate that it is likely to be immobile in soil (Table 3). Bifenthrin
is relatively insoluble in water. However, because it is attached to colloidal particles it may be
transported with them into waterways and groundwater. Bifenthrin will exist in the atmosphere
in particulate and vapour phases, where vapour phase bifenthrin is degraded by hydroxyl
radicals and ozone. Because pyrethroids are readily degraded by microorganisms, it is likely
that microbial degradation of bifenthrin will occur.
Alpha-cypermethrin (BASF Australia Ltd; FM C Chemicals Pty Ltd) is a racemic mixture of
two of the four cis isomers – the (1R, cis)S and (1S, cis)R isomers of cypermethrin. Example
12
products are Stedfast and Prevail, which are registered in Australia for use as a chemical
barrier.
Alpha-cypermethrin
C 22 H19 C12 NO3
[CAS 67375-30-8]
(S)- alpha-cyano-3-phenoxy benzyl (1R,3R) 2,2-dichlorovinyl)-2,2- dimethylcyclopropane
carboxylat e and (R) - alpha cyano - 3-phenoxy
benzyl (IS,3S)-3-(2,2 dichlorovinyl)
cyclopropane carboxylate
Property
Group
Value
Synthetic pyrethroid ester
White, cream yellow or colourless crystalline
powder, solid or liquid (EC)
155–180o C (EC)
78o C (powder)
Melting point
Figure: Meghmani
Organics Fact Sheet
Source
Alpha-Cypermethrin
MSDS 1999
-7
Vapour pressure
(mm Hg at 25o C)
1.7×10
Solubility in water at 25o C
(mg/L)
Octanol-water coefficient
(Log Kow)
Metabolites
Half-life
0.005–0.01
5.16
cis-cyclopropane carboxylic acid
hydrolysis half-li fe 20 – 29 days
Extremely low
OSU Ext. Pesticide
Table 4. Summary of the physicochemical properties of alpha-cypermethrin
13
Deltamethrin (AgrEvo Environmental Health, Inc.) – Trade names internationally include
Butoflin, Butoss, Butox, Cislin, Crackdown, Cresus Decis-Prime. Deltamethrin (Table 5) is
used in Kordon-impregnated barrier products. In Australia deltamethrin is sometimes, but not
often, used in termiticides.
Deltamethrin
C 22 H19 Br2 NO3
[CAS 52918-63-5]
(S)-cyano-3-pehoxybenzyl (1R)-cis-3-(2,2dibromovinyl)-2,2-dimethylcyclopropane
carboxylat e
Property
Group
Melting point
Vapour pressure
(mm Hg at 25o C)
(Log Kow)
Value
Powder - white or colourless, crystalline
98-101o C
1.5 x 10--8
Source
EXTOXNET
WHO Data Sheet
EXTOXNET
<0.1
4.6
Table 5. Summary of the physicochemical properties of deltamethrin
4.3 The chloronicotinyls (nicotinoids)
The nicotinoids are a relatively new class of insecticide, modelled on natural nicotine.
Imidacloprid (Bayer Cropscience Pty Ltd) products internationally include Admire, Condifor,
Gaucho, Premier, Premise, Provado, and M arathon. Only Premise is registered for use against
termites in Australia. Imidacloprid is a systemic, chloro-nicotinyl that works by interfering with
the transmission of stimuli in the insect nervous system. Specifically it causes blockage of the
nicotinergic neuronal pathway, leading to acetylcholine accumulation – resulting in the insect's
paralysis, and/or death. Imidacloprid-based insecticide formulations are available as dustable
powder, granular formulations, seed dressing (flowable slurry concentrate), soluble
concentrate, suspension concentrate, and wettable powder. It is currently registered in Australia
for post-construction applications only.
14
Hydrolysis and aerobic soil metabolism data indicate that imidacloprid is persistent and mobile
with a tendency to leach. Under some circumstances contamination of groundwater is possible
(EPA Imidacloprid Pesticide Fact Sheet 1994). Imidacloprid can be translocated via plant roots.
When used to form applied termiticide barriers, consideration should be given to the risk of
product losses due to plant uptake, and possible ingestion by grazing animals.
Imidacloprid
C 9 H10ClN5 O2
[CAS 13826-41-3]
1-(6-chloro-3-pyridylmethyl)-Nnitroimidazolidin-2-ylideneamine, 1-[(6-chloro3-pyridinyl)methyl]-N-nitro-2imidazolidinimine
Property
Group
Melting point
Vapour pressure
(mm Hg at 25o C)
Solubility in water at 20o C
(mg/L)
Value
Chloronicotinyl
Colourless to light yellow crystals or powder
136.4-143.8oC
1.5 X 10-9
(Log Kow)
(Koc)
Metabolites
3.7 at pH 7.8
Half-life
•
•
High
510
132–310
6-chloronicotinic acid – eventually breaks down
in soil to CO2
Soil photolysis half-li fe 38.9 days
355 days in water (pH 9)
Table 6. Summary of the physicochemical properties of imidacloprid
15
Figure: Bloomquist 1999
Source
EPA Fact Sheet
4.4 The phenyl pyrazoles (fiproles)
Fipronil (Bayer Cropscience Pty Ltd.) - is a phenyl pyrazole, a new class of chemical (Table 7).
Products internationally include Termidor SC and Termidor 80 WG. Fipronil has been under
consideration by the NRA for registration in Australia as termiticide and gained registration for
protection of structures from subterranean termite attack in October 2002. It was previously
used in Australia only for topical flea and tick control on dogs (and in agriculture e.g. Regent).
Fipronil is a disruptor of the insect central nervous system via the GABA (γ-aminobutyric acid)
channel, acting with contact and stomach action. It blocks the GABA-gated chloride channels
of neurons in the central nervous system, resulting in neural excitation and death of the insect.
Fipronil
C 12 H4Cl2 F6 N4 O4 S
[CAS 120068-37-3]
5-amino-1-[2,6-dichloro-4(tri fluoromethyl)phenyl]-4[(tri fluoromethyl)sul finyl]-1H-pyrazole-3carbonitrile
Property
Group
Melting point
Vapour pressure
(mm Hg at 25o C)
(Koc)
(Log Kow)
Metabolites
Value
Phenyl pyrazole
White powder
195.5 to 203oC
2.8 x 10-9
1.9 (distilled water), 2.2 (pH 9)
803
4.01
•
•
•
Half–life
Figure: Ware 1999
Reference
NRA Fipronil Evaluation
In soil: RPA 20076 (amide), MB46513
(fipronil-desul finyl), and RPA 104615
In water: MB 45950 (sulphide)
Under aerobic conditions RPA 200766
and MB 46136 (sulfone)
•
•
•
10–130 hours in water
45–530 hours in soil
122–128 in oxygenated soil
•
116 – 130 days in anaerobic conditions
Table 7. The physicochemical properties of fipronil summarised.
16
Mulrooney et al. 1998
Mulrooney et al. 1998
National
Telecommunication
Network (NTPN)Fact
Sheet
NTPN Fact Sheet
4.5 Growth (chitin synthesis) inhibitors
Hexaflumuron (Recruit II termite bait – Dow Agrosciences) (C16H8Cl2F6N2O3) [CAS 8647906-3]: A benzoylurea insecticide, which is a chitin synthesis inhibitor, used in bait stations.
Hexaflumuron binds tightly to soil particles. Similar are Triflumuron (Intrigue termite dust –
Bayer Cropscience) (C15H10ClF3N2O3) [CAS 64628-44-0], and Chlorfluazuron (Requiem
termite bait) (C20H9Cl3F5N3O3) [CAS 71422-67-8], chitin synthesis inhibitors used in bait
stations.
4.6 Other chemicals
Arsenic trioxide (As4O6) [CAS 1327-53-3], is used in bait and switch management programs,
and for direct dusting onto nests. The arsenic content in these dusts ranges from 379 g/kg to
500 g/kg.
Methyl bromide (H3Br) [CAS 74-83-9] gas is used to fumigate drywood termite infestations.
It is pumped into sealed buildings or wooden articles.
Boron – new boron complexes for wood protection are being developed with some success by
CSIRO and the Centre for Green Chemistry at M onash University in Australia. With leachresistant boron binding to wood as the ultimate aim, high levels of mortality for C.
acinaciformis have been recorded for particular boron formulations (Humphrey et al., 2002).
Boron products include Boracol (Osmose Australia Pty Ltd), which is registered for use for
pre-treatment and remedial treatment of timber against decay (fungal) and insects. Constituents
include M ono ethylene glycol (886 g/kg). Boron is present in the form of disodium octoborate
tetrahydrate (52 g/kg) and benzalkonium chloride (12 g/kg). Boron-impregnated rods
(Preschem Rail Rods) are inserted into wooden railway sleepers as a slow release preservative
and termite repellent.
Impregnated wood preservatives include mixtures of copper, arsenic and other chemicals
(i.e. chromium) used for protection against termite and borer attack. Generally, these are used
in pressure impregnation of new wood e.g. Tanalith CP Paste is a mixture of arsenic (95.8 g/L),
chromium (135.199 g/L) and copper (75.699 g/L). Other products approved for use in Australia
include Protim 70, a mix of white petroleum spirit (613 g/L), copper naphthenate (170 g/L) and
permethrin (2.599 g/L). Combinations of disodium octoborate tetrahydrate and benzalkonium
chloride are also used in formulations of insecticidal wood preservative.
Creosote (creosote, coal tar) external timber preserving oil (Davco; Koppers Arch Wood
Protection Australia Pty Ltd; Protectex Chemicals Pty Ltd.) is also used to preserve wood, and
is painted onto external timber as a means of preservation and a termite deterrent. Creosote was
typically used in combination with aldrin.
Mirex (C10Cl12) [CAS 2385-85-5] (M irant Pty Ltd). M irant (M irex 2.0 g/kg) and M irex 6 g/kg
baits are the only organochlorine cyclocompounds termiticide currently used for termite control
in Australia. They are registered for use only in the Northern Territory and Western Australia
for M. darwiniensis control (registered currently to June 2003), primarily for use in the
prevention of termite infestations of fruit trees under cultivation.
17
5. Migration and behaviour of currently used termiticides in soils
Environmental variables are important, particularly in terms of transport, degradation and
volatilisation of termiticides. Following application, termiticides can be lost from the original
application site via lateral and vertical movement into surrounding soil and groundwater. It is
possible that these chemicals will also be transferred to local biota and animals (Figure 1).
The movement of pesticides through soil largely depends on the physical properties of
individual chemical actives, the presence of water and biota and organic material, as well as the
solvent/s that have been used in the pesticide formulation. Soil characteristics, pH and the
presence of organic matter play major roles in determining the persistence and efficacy of
chemicals. The half-life of a chemical in the soil will depend on a combination of these factors
and will be influenced by the biota present. Sandy soils with low biota/low organic content and
wet conditions generally result in increased transport, whereas those with high clay and organic
content tend to not allow chemical migration as readily. The mineral content of the soil will
influence degradation, by affecting adsorption rates or catalysing decomposition. Termiticides,
in particular the organophosphates, can be lost from the soil through movement of volatiles into
the air due to their significant vapour pressures at ambient temperatures.
Soil properties – organic content, silt and clay content, pH and cation exchange capacity – may
affect the bioavailability and dispersal of pesticides. In comparisons of different soil types
treated with imidacloprid, pesticide effects on R. flavipes were greatest in sand and reduced in
silty clay loam soils (Ramakrishnan et al., 2000). Testing of four soil types with six termiticide
formulations indicate that soils have a significant influence on the efficacy of the chemicals
(Forschler and Townsend, 1996). Of the termiticides tested (including chlorpyrifos, fenvalerate,
cypermethrin and permethrin), all had concentrations lethal to termites that were at least seven
times lower in sandy soils than in sandy loam or sandy clay loam (Forschler and Townsend,
1996). M urray et al. (2001) examined the stability of chlorpyrifos in six Australian soil types.
Soil pH had no effect on the rate of degradation. In contrast, acidic soils with low clay and
organic content in Texas, USA, were found to be the most stable in terms of remaining
bioavailability of pesticides, while alkaline soils with high clay content and organic
compositions higher than 1% were least effective in retaining termiticide residuals over time
(Gold et al., 1996).
18
6. The efficacy and persistence of currently used termiticides
The physicochemical properties of termiticides directly influence their behaviour, persistence
and bioavailability after application (see tables in section 4 for summaries of physicochemical
properties).
Australian evaluations of the organophosphates in soils suggest an effective life for
chlorpyrifos of 7 to 12 years if covered, to as little as 4 years when exposed to the elements
(Lenz et al., 1988), and suggest that in tropical Australia, the chemical be reapplied at 3-year
intervals. A field study of leaching and degradation of pesticides (including chlorpyrifos,
chlorthal dimethyl, fenamiphos, fenamiphos plus metabolites, linuron, metalaxyl, metribuzin,
prometryne, propyzamide and simazine) in coastal sandy soils (pH 5.3) in Western Australia
demonstrated that degradation rates vary widely between pesticides (Kookana et al., 1995). In
this study, chlorpyrifos degraded significantly, but did not move considerably, and it was
concluded that it was unlikely to reach groundwater (Kookana et al., 1995).
A study of 6 termiticides (bifenthrin, chlorpyrifos, cypermethrin, fenvalerate, permethrin and
isofenphos) applied to different soil types in Texas, USA, demonstrated significant differences
in effectiveness (as measured by termite activity), bioavailabilty and residue. The most stable
over 5 years were permethrin and fenvalerate. Isofenphos was the least stable with significant
loss of activity within 24 months after application (Gold et al., 1996). Barrier efficacy tests of a
range of termiticides (Dursban, Equity, Dragnet, Prevail, Biflex, Pryfon, Demon, PP321 and
Sumithion) in the USA indicate that while all formulations provide equal protection against R.
flavipes, C. formosanus was able to tunnel deeper into sand treated with organophosphates than
in sand treated with pyrethroids (Su et al., 1993). Isofenphos lost effectiveness within 1 year,
and rapidly degraded – probably as a result of alkaline sand (pH 8.1), microbe activity and high
rainfall (Su et al., 1993).
Pyrethroids (bifenthrin, cypermethrin, lambda-cyhalothrin and permethrin) appear to provide
longer protection than organophosphates (chlorpyrifos, fenitrothion and isofenphos). According
to 5-year field trials in Florida, USA, against R. flavipes (Su et al., 1999), permethrin had the
longest half-life (21.9 months) of the pesticides examined. M icroencapsulated formulations
generally result in longer persistence. Little published Australian data is publicly available on
the persistence and efficacy of other termiticides.
7. S olvents
The solvents used to formulate commercially available termiticides are of interest, since alone
or in combination with other chemicals they may have significant effects on the active
ingredients and their environmental fate. In some cases, solvents may cause toxic effects.
Unfortunately, the solvents used in pesticide formulations are often treated as inerts, and not
listed in detail on pesticide labels. It is often difficult to obtain information about the exact mix
of adjuvants and solvents used in formulations because of commercial in confidence. Solvents
and adjuvants used may include a range of petroleum distillates, isopropanol, methanol,
toluene, xylene, penetrants, stickers (film extenders), surfactants, detergents, dusts, emulsifiers
and anticaking agents. Because particular combinations of solvents and adjuvants used in
formulations may give companies a competitive advantage, their inclusion in labelling is often
sparse. In many cases continuous subtle changes to the formulations of products are made to
suit particular purposes, resulting in several non-identical products sharing the one original
name. Because of the varied requirements for termiticides, solvents may not always be suited to
19
all applications and “boutique” formulations may be needed for specific uses. For example,
around power poles, a formulation is required to remain in a restricted area and not spread
away from the pole when applied, whereas under the slabs of houses it is desirable that the
termiticide be distributed evenly underneath the slab.
It is possible that there may be interactions leading to additive or reduced-level effects,
between pesticides and the components of their formulations. For example, Axelrad et al.
(2002) found synergism between chlorpyrifos and regular spirit solvent and also with
chlorpyrifos and pyrethrum, but additive effects (in terms of neurological toxicity) in other
combinations of chlorpyrifos and pyrethrum with individual components of a commercial
formulation. In addition, solvents may influence the movement and action of the active
ingredient through soils and water. There is some evidence that solvents alone may affect
termites. For example, sand treated with solvents alone may be toxic to termites – with 24 to
86% of Reticulitermes hesperus Banks killed after 24 hours of exposure to the air-dried solvent
treated sand (Rust and Smith, 1993).
8. Toxicology and risks to human health from termiticide usage
In Australia, termiticides must be approved and registered by the NRA. Prior to registration for
use in Australia, a proposed pesticide must undergo an assessment process, which includes
assessment for possible effects on public health and on the environment. Toxicity and potential
public health issues are assessed by the Commonwealth Department of Health, occupational
health and the National Occupational Health and Safety Commission (NOHSC) assess safety
issues, and Environment Australia (EA) assesses environmental safety. The NRA assesses
chemistry and efficacy. Toxicology data for termiticides is derived largely from animal studies,
and involve doses that are generally much larger than those for likely human exposures.
Toxicity tests identify ‘no observable effect levels’ (NOELs) in animals, and these are used to
establish acceptable limits for exposure in humans at which no adverse health effects would be
expected – the Acute Reference Dose (ARD) and Acceptable Daily Intake (ADI). Because
formulations are designed to enhance environmental persistence (in order to be effective
against termites for longer periods of time), it is highly desirable that long-term effects on
environmental and public health under Australian conditions be investigated with emphasis on
long-term sublethal effects, which are not assessed in acute studies.
When applied according to safety guidelines and manufacturers’ recommendations, the
risk of poisoning or exposure to high levels of termiticides is minimal. Trace residues
nonetheless can be sometimes found in water. Indoor air pollution caused by pesticides may be
of concern in buildings with poor ventilation, resulting in long-term exposure to low levels of
chemicals. Chlorpyrifos was recorded in indoor air in Japan, and did not decrease 5 years after
application for termite control (Yoshida et al., 2000). Japanese investigators found that levels
3
3
of chlorpyrifos and S-421 in indoor air ranged up to 0.258 µ-g/m and 0.174 µ-g/m
respectively in houses where chlorpyrifos had been applied to building timbers for termite
control (Katsura et al., 1996). In Western Australia, 19 of 22 houses monitored for pesticide
levels had detectable levels of pesticides in indoor air – in order of frequency: heptachlor;
dieldrin; chlordane; aldrin and chlorpyrifos. Although chlorpyrifos was least frequently
3
detected, the mean concentration of 2554 µg/m was significantly higher than that of other
pesticides (Dingle et al., 1999). These levels are well below the National Academy of Sciences
3
guideline level for ambient air of 10 µg/m and are considered not to pose an acute threat to
public health. However, data on long-term exposure to low levels is limited
20
Chlorpyrifos (ADI 0.003 mg/kg/day, NOEL 0.03 mg/kg/day TGA, 2002) is moderately toxic
to humans. Poisoning from chlorpyrifos can affect the central nervous system, the
cardiovascular system, and the respiratory system. It is a skin and eye irritant. While some
organophosphates are readily absorbed through the skin, studies suggest that skin absorption of
chlorpyrifos is limited in humans. Symptoms of acute exposure to organophosphate (and other
cholinesterase-inhibiting compounds) may include the following: numbness, tingling
sensations, loss of coordination, headache, dizziness, tremor, nausea, abdominal cramps,
sweating, blurred vision, difficulty breathing or respiratory depression, and slow heartbeat
(EXTOXNET Chlorpyrifos Pesticide Information Profile). Very high doses may result in
unconsciousness, incontinence, convulsions and fatality.
Some organophosphates may cause delayed symptoms beginning one to four weeks after an
acute exposure, which may or may not have produced immediate symptoms. In such cases,
numbness, tingling, weakness, and cramping may appear in the lower limbs and progress to incoordination and paralysis. Improvement may occur over months or years, and in some cases
residual impairment will remain. P lasma cholinesterase activity levels may be inhibited when
chlorpyrifos particles are inhaled. The EPA (USA) analysis found exposure to Dursban
(chlorpyrifos) on the skin, in food, or by inhaling it could be harmful to human health. The
EPA said it had a “particular concern” with Dursban poisoning cases reported to federal
officials. Repeated or prolonged exposure to organophosphates may result in the same effects
as acute exposure, including the delayed symptoms.
Chlorpyrifos is readily absorbed into the bloodstream through the gastrointestinal tract if
ingested, through the lungs if it is inhaled, or possibly through the skin if there is dermal
exposure. In humans, chlorpyrifos and its principal metabolites are eliminated rapidly.
Chlorpyrifos primarily affects the nervous system through inhibition of cholinesterase. Animal
studies suggest that chlorpyrifos is rapidly absorbed and metabolised (to TCP), and the parent
compound and metabolite are rapidly excreted in urine. In orally dosed pregnant rats (at 14 to
18 days gestation) AchE and BuChE activities were inhibited significantly in both maternal and
foetal brains one hour after ingestion (Ashry, K.M . et al., 2002). The dose used here was
50 mg/kg, which is 61% of the LD50 for female rats. In addition, neonatal rats orally
administered much lower rates of chlorpyrifos, at 1 mg/kg or 5 mg/kg, demonstrated
deficiencies in cataechloaminergic synaptic function persisting into adulthood (Slotkin et al.,
2002).
Current evidence indicates that chlorpyrifos does not adversely affect reproduction, and
available evidence suggests that chlorpyrifos is not teratogenic. Chlorpyrifos is not considered
to be a carcinogen, nor does it appear to have reproductive effects at levels of up to 2 mg/kg per
day (EPA Pesticide Factsheet, Chlorpyrifos 1984). There is no available evidence that
chlorpyrifos is mutagenic. However, Rahman et al. (2002) report dose-dependent DNA damage
detectable in mice 24 hours after being fed chlorpyrifos at doses of 0.28 to 8.96 mg/kg body
weight.
Assessment of neurological function in a group of pesticide applicators exposed to chlorpyrifos
(n=191) compared to non-exposed controls (n=189) revealed that there was no significant
difference in clinical examinations. However, the exposed group under-performed in pegboard
turning and postural sway tests and reported significantly more symptoms (memory problems,
fatigue, loss of muscle strength). Eight exposed subjects who had reported prior chlorpyrifos
poisoning had low performance on tests (Steenland et al., 2000).
21
The pyrethroids are not considered extremely toxic to humans. Exposure can cause skin, eye
and respiratory irritation, and sometimes cause allergic reactions. Tingling sensations in the
hands and face may follow exposure. Bifenthrin (ADI 0.01 mg/kg/day, NOEL 1 mg/kg/day
TGA, 2002) and alpha-cypermethrin (ADI 0.05 mg/kg/day, NOEL 4.7 mg/kg/day TGA,
2002), can cause nerve damage, resulting in tremors, difficulty walking, agitation and abnormal
gait. Bifenthrin is absorbed through intact skin if applied topically. It is moderately toxic to
mammals when ingested, and large doses may cause incoordination, tremor, salivation,
vomiting, diarrhoea, and irritability to sound and touch (EXTOXNET Bifenthrin Pesticide
Information Profile). Bifenthrin has low dermal toxicity and is non-irritating to the skin and a
low irritant to the eyes (FM C, 2000). Permethrin (ADI 0.05 mg/kg/day, NOEL 5 mg/kg/day
TGA, 2002), a type I pyrethrum, affects the central and peripheral nervous system, and
exposure may cause tremors, salivation, hyperexcitability and paralysis. Deltamethrin (ADI
0.01 mg/kg/day, NOEL 1 mg/kg/day TGA, 2002) poisoning results in different symptoms than
those of other pyrethroids – mammals undergo salivation and writhing and rolling convulsions,
and other type II motor symptoms. Symptoms of deltamethrin poisoning in humans include
convulsions, ataxia, tremors and vomiting.
Imidacloprid (ADI 0.06 mg/kg/day, NOEL 6 mg/kg/day TGA, 2002) poisoning is likely to
cause similar signs to nicotinic poisoning such as fatigue, twitching, cramps, difficulty
breathing and muscle weakness including the muscles necessary for breathing. Toxic effects
are listed as reduced muscle tone, tremors, apathy and muscle cramps with associated
difficulties breathing in severe cases (TGA, 2001). Imidacloprid is not irritating to the skin and
does not cause skin sensitisation. Evidence of liver toxicity, tremors and weight loss were seen
in animals fed high doses (TGA, 2001).
Hexaflumuron (ADI 0.02 mg/kg/day, NOEL 2 mg/kg/day TGA, 2002) has a low oral LD50 in
rats at >5000 mg/kg, indicating that it is not particularly toxic to mammals. Toxicity tests
conducted in animals indicate that hexaflumuron is an irritant to eyes (in rabbits), and skin. The
ingredients are not listed as carcinogenic, and it is not recorded to have caused reproductive
damage in animals. Triflumuron has similar toxicological characteristics (TGA, 2001). The
chitin synthesis inhibitors have the advantage of low levels of toxicity to mammals (oral LD50
in rats of >5000 mg/kg), but are very toxic to aquatic animals (NPTN), and should not be used
in situations where it may enter waterways or groundwater.
Fipronil (ADI 0.0002 mg/kg/day, NOEL 0.02 mg/kg/day TGA, 2002) is irritating to the skin
and eyes. It is toxic by oral, dermal and inhalation routes. It can cause skin irritation in cats and
dogs, and may cause reproductive effects such as decreased mating, reduced litter size and
decreased postnatal survival. Fipronil is not mutagenic (PAN, 2000). The photodegradate M B
46513 has a higher acute toxicity to mammals than fipronil itself by a factor of approximately
10 (WHO, 1998).
Fipronil and its breakdown products are neurotoxic to mammals. There is no evidence of
fipronil causing birth defects, but it may cause a delay in development at high doses. Fipronil is
carcinogenic to rats at doses of 300 ppm, causing thyroid cancer related to disruption in
thyroid-pituitary status. It is classed as a possible human carcinogen based on the rat
carcinogenicity study (PAN, 2000). Studies have shown that there is potential for
bioaccumulation of the photodegradate M B 46513 in fatty tissues (PAN, 2000).
Arsenic trioxide is highly toxic, but because it is used in bait stations or applied as a dust
directly to nests, potential for exposure is limited. Signs of poisoning include stomach
cramping, vomiting and diarrhoea, and long-term effects of exposure include increased
22
incidence of cancers of the liver, lung, skin, bladder and kidneys (TGA, 2001). Arsenic has also
been identified as genotoxic and teratogenic.
9. Potential effects of termiticides on non-target species
In most cases, termiticides are unlikely to cause significant environmental effects, providing
that they are applied according to recommended application rates and methods and the
recommended safety precautions are taken. Contamination of water surfaces and runoff should
be avoided in all cases.
Termiticides may present hazards to wildlife if they are absorbed or ingested. Unfortunately, as
insecticides, termiticides are also toxic to beneficial insects such as bees. Acute affects include
poisoning, resulting in a range of signs, from minor illness and behavioural or reproductive
changes to death depending on the levels and means of exposure. The greatest hazards are
posed to aquatic organisms through contamination of waterways via runoff or spills. Soil
organisms, such as earthworms, which play a significant role in soil ecosystems are often
exposed to termiticides, which may have lethal or sub-lethal effects depending on levels of
exposure.
Current guidelines for Australian organisms are largely derived from overseas data, sometimes
with “correction factors” applied to suit Australian conditions. However, the differences in
persistence between overseas and Australian soils indicate that experimental evidence needs to
be gathered in order to support this approach. There are significant gaps in current knowledge
regarding the long-term effects of termiticides in the Australian environment. Although
considerable amounts of data have been accumulated for overseas species (see Tables 8 and 9),
particularly for chlorpyrifos, in many cases these are not always easily related to local
conditions. It is important to note that toxicity levels for pesticides are generally based on
animal studies, usually at exposure levels much higher than people would be exposed to, and
may not be directly applicable to humans.
Chlorpyrifos is highly toxic to freshwater fish, aquatic invertebrates and estuarine and marine
organisms. Because of its persistence in aquatic sediments, chlorpyrifos may represent a hazard
to sediment feeders. Fish species are differentially affected by chlorpyrifos, with some species
(e.g. Gambusia) surviving contaminations that killed several other species. Such differences in
species susceptibility are likely to be the result of species differences in the sensitivity of brain
acetylcholinesterase to inhibition by chlorpyrifos-oxon (Carr et al., 1997). The ecotoxicology
of chlorpyrifos, including comprehensive LC50 data for many species, has been extensively
reviewed by Barron and Woodburn (1995).
Cladocera, Ceriodaphnia dubia (Richard, 1894), exposed to binary and tertiary mixtures of
chlorpyrifos, profenofos and endosulfan were increasingly impaired reproductively than when
exposed to single pesticides (Woods et al., 2001). In a mixed Australian zooplanktonic
-1
community, chlorpyrifos at single (20 µg/L ), and multiple doses, decreased cladoceran
densities in laboratory tests, but copepod densities increased commensurately, while
phytoplankton density did not change in response to chlorpyrifos. Continuous, low doses of
chlorpyrifos (1 µg/L-1) had no measurable effect (Simon and Helliwell, 1997).
23
Sarneckis and Kumar (2001) tested two commercial formulations of chlorpyrifos, Lorsban and
wettable powder, on embryos and tadpoles of Littoria ewingii, the brown tree frog, and
Xenopus laevis, the South African clawed frog. Lorsban was found to be more toxic than the
wettable powder, and X. laevis was more sensitive than L. ewingii to both formulations.
Pesticide-exposed embryos developed abnormalities varying from blistering, spinal curvature,
reduced growth and oedema. The authors found that there was a dose-response relationship
between AchE inhibition, malformations and chlorpyrifos exposure in tadpoles – 96h
LC50/EC50 corresponded with 80–90% AchE inhibition. M ixture toxicity tests using
chlorpyrifos plus profenfos/or endosulfan resulted in synergistic or additive effects when tested
on X. laevis frogs (Woods and Kumar, 2001). Such mixtures may occur when aquatic systems
become polluted, and thus mixture toxicity tests reflect actual pollution of aquatic systems in a
more realistic way than do experiments using individual toxicants (Woods and Kumar, 2001).
Cholinesterase activity in earthworms, and the stability of the lysosomal membrane, are
sensitive to organophosphate exposures (Booth et al., 2000). For earthworms, chlorpyrifos in
soils was toxic at LC50 of 104 to 1174 mg/kg of soil (M a and Bodt, 1993). However, the
authors recorded wide variation in toxicity.
The pyrethroids are relatively non-toxic to birds, but very toxic to mammals if swallowed.
They are highly toxic to invertebrates, fish and aquatic organisms. The pyrethroids are much
more toxic to aquatic than terrestrial organisms because they inhibit ATPase enzymes, which
are essential for maintaining the concentration gradients required by cells for osmoregulation
and the maintenance of ionic balances in an aquatic environment. Fish and other gilled animals
are particularly at risk because of the large exposed surface areas that gills provide. Bifenthin
has a high bioconcentration factor in bluegill sunfish (Bifenthrin M SDS) and as evidenced by
its Log Kow of >6, and this along with its persistence might lead to exposure risks in apex
species, particularly those that feed on sediment dwelling organisms. The pyrethroids are also
extremely toxic to bees.
Imidacloprid is highly toxic to some species of birds (e.g. house sparrows, and pigeons), but
acute toxicity in birds varies widely between species. It has caused eggshell thinning, decreased
weight and reduced egg production and hatching success in some bird species (EPA Fact Sheet;
J. Pesticide Reform 2001, Imidacloprid Fact Sheet). Imidacloprid is also highly toxic to fish
and other aquatic organisms, with LC50 levels for mysid shrimp of 37 ppb and behaviour
effects noted in surviving shrimp (EPA evaluation data in Pesticide Reform 2001, Imidacloprid
Fact Sheet). Imidacloprid is acutely toxic to earthworms, with LC50 levels of 2–4 ppm in soils
for Eisenia foetida (Zang et al., 2000). Imidacloprid’s ability to move through soil relatively
easily poses concerns for potential contamination of waterways and groundwater. Imidacloprid
is absorbed by plants from the soil through roots and therefore there may be a risk of exposure
to herbivores.
Hexaflumuron has low levels of toxicity to mammals (oral LD50 in rats of >5000mg/kg), but is
very toxic to aquatic animals (NPTN) and to bees (TGA, 2001).
Fipronil is highly toxic to game birds, fish and aquatic invertebrates, and moderately toxic to
waterfowl and mammals. The metabolites of fipronil are very much more toxic. The metabolite
M B 461 is more highly toxic to birds, and the metabolites M B 46136 and M B 45950 are more
highly toxic to freshwater invertebrates than fipronil itself (PAN, 2000).
24
10. Incidents involving termiticides in southeast Queensland
Chlorpyrifos has been implicated in many chemical-related urban fish kills, and bifenthrin has
been responsible for some. The increasing use of bifenthrin has resulted in an increasing
number of incidents involving bifenthrin. Identifying the source of the chemical is often
difficult. The following are incidents reported in the media during 2001 and 2002, and
documented by EPA (Aust.) press releases.
•
January 2001: Swan Lake canal estate, Gold Coast – pest control company driver
washing spillage into a stormwater drain. Chlorpyrifos (Dursban) subsequently
identified at 100 times the lethal dose for fish in the canal water. Over 1000 fish killed.
•
February 2001: Bifenthrin (0.125 mg/kg) was found in oysters from Redcliffe
waterways (Keys and M ortimer, 2001), at well above Food Standards Australia and
New Zealand (FSANZ) food standards code for maximum residue levels (0.05 mg/kg).
The source of this contamination is not known, but it is likely to be as a result of runoff
from nearby canal estate building sites.
•
February 2001: Loders Creek, Southport – fish kill followed by tests revealing high
concentrations of chlorpyrifos. The source of contamination is not known, but it is
likely to be as a result of runoff from nearby canal estate building sites.
•
M arch 2001: Oxley Creek tributary, Brisbane – chemicals leaked through storm drains
to the creek in runoff following a fire at Barmac Industries at Rocklea. Chemicals
included insecticides and herbicides, requiring water to be pumped from the creek by
the Queensland EPA, to prevent contaminated water reaching O xley Creek.
•
2001–2002: Gold Coast – Complaints from residents about the taste and odour of tap
water following termiticide treatment. Permeation through plastic water pipes by
solvents is suspected as the cause. Analysis of water samples indicated the presence of
volatile organics, C3 and C4 substituted benzenes and aromatic hydrocarbons. The
termiticides chlorpyrifos and bifenthrin were also identified, but were not quantified
and so it is difficult to make health risk assessments regarding them. In cases where the
polyethylene pipes were replaced with copper pipes the contamination ceased,
suggesting that there was some permeation of solvents through the polyethylene pipes.
•
Contamination of local waterways: A reported decline in the abundant species at the
Boondall wetlands prompted an examination of local organisms for chemical
contamination in 1995 (M ortimer et al., 1997).
•
As well as evidence of contamination by heavy metals, in some sites bifenthrin and
chlorpyrifos were found in sediments around Brisbane waterways (Mortimer et
al.,1997). Oysters in the Redcliffe area have tested positive for the presence of
chlorpyrifos at every site tested, although the latest results were negative for bifenthrin
(Keys et al., 2002).
Termiticides were also in the news in 1999, and consumer confidence in the pest control
industry was shaken when more than 5000 new homes were allegedly treated with watereddown termiticides instead of the required treatment. In 1999 the BSA launched a prosecution
against the company involved for improper termite works as a result.
25
11. Potential new chemical treatments
There are chemicals under consideration (or reconsideration) or being evaluated for use as
termiticides in Australia that are currently used with varying success in other countries. One
of the more interesting variations is Silafluofen (C25H29FO2Si), an insecticide (pyrethroid
ether) containing silicon, used in Japan for soil and timber treatments against termites and
other pests since 1991. It has become popular because it has low toxicity to fish and
mammals, and it is highly stable chemically (Nakayama et al., 2001). Antitermitic plastic
sheeting and antitermitic heat insulators have been developed by impregnating silafluofen into
plastic film and polystyrene foam.
12. Biological control
The protected underground nature of termite colonies makes them a poor candidate for
biological control. A few parasitoids are known but they appear to have limited potential for
controlling, preventing or treating termite populations. Viruses, bacteria, protozoa,
nematodes, bacteria and most fungi have shown little promise in termite management
(Culliney and Grace, 2000). Biological control attempts using bacteria, fungus (Metarhizium
anisopliae (M etsch) and nematodes (Heterorhabdis spp. and Steinernema spp.) have had
some success in experimental trials (Peters and Fitzgerald, 1998).
Predators
Ant species have been proposed as possible biological control agents for termites under
certain conditions. Kenne et al. (2000) proposed the use of the generalist ant Myrmicaria
opaciventris as a biological control agent for termites in sugarcane plantations.
Semiochemicals
Semiochemicals from Ochetellus (previously Iridomyrmex) glaber (M ayr) worker ants
strongly repel C. formosanus termite workers. Dichloromethane extracts taken from extracts
of whole ants used to treat sand, resulted in a barrier that was not penetrated by termites
(Cornelius and Grace, 1994). It is possible that ant semiochemicals could provide a source of
alternatives for future termite control.
Monoterpenoids
M onoterpenoids are potentially useful for the development of new insecticides because they
have low mammal toxicity – may be plant or animal semiochemicals. Cornelius et al. (1997)
found that monoterpenoid alcohols particularly eugenol were effective as termiticides against
C. formosanus, and that termites would not tunnel through eugenol, or geraniol, treated sand
barriers for 5 days.
Entomopathic fungi
The fungus Metarhizium, when ingested by an insect, penetrates the cuticle causing mortality.
M. anisopliae has been isolated from diseased nests of R. flavipes in Canada. Subsequent
bioassays have shown that the fungus is spread rapidly to healthy termites through contact,
and is able to cause 100% mortality within 24 hours (Zoberi, 1995). In laboratory experiments
with C. formosanus, where strains of Beauvaria bassiana (Balsamo) and M. anisopliae were
exposed to foraging termites, termites did not avoid the fungal baits.
26
Exposure to M. anisopliae strains resulted in rapid termite mortality while the B. bassiana
strain resulted in slower but increasing mortality (Delate et al., 1995b; Jones et al., 1996). C.
brevis is susceptible to M. anisopliae, with mortality 4 weeks after exposure at 93 to 100%
(Nsar and M oein, 1997). In Australia, some strains of Metarhizium have been identified by
the CSIRO as potentially able to control termites (CSIRO M edia release 99/129 1999). The
fungi are being produced and tested in conjunction with the company Seed, Grain and
Biotechnology Australia in Victoria.
It may be possible to infect forestry trees with fungi in order to control the termites that attack
them. Suzuki et al. (1996) discuss field application of fungi, which resulted in no clear effects
on the majority of trees (Pinus luchuensis). Aspergillus niger and Paecilomyces fumoroseus
as well as B. bassiana and M. anisopliae show promise for control of termites (Suzuki et al.,
1996).
Entomopathic fungi hold promise as baits for termite management. Grooming and social
interactions have potential to spread fungus infections throughout colonies. However, termites
may avoid fungus conidia and remove and bury fungus-killed individuals, which along with
defensive secretions may limit the spread of the fungus (Rath, 2000). Direct application to
nests has resulted in complete mortality. However, feeding sites and bait stations have not
shown similar success and effectiveness in the treatment of buildings and timber structures.
There is currently a commercial product available in the USA. Bio-Blast uses fungal
treatment, which is passed to other termites through a horizontal transfer effect.
13. Alternative treatments and management tools
Soil insecticide barriers have been the single most important means of controlling termites
over the last 50 years, however limitations of current soil termiticides and the popularity of
slab-on-ground housing, along with increased awareness of potential environmental and
health affects has led to a search for alternatives.
Monitoring and baiting programs
M onitoring stations are used to detect termite activity. When termite activity is detected, the
monitoring station baits may be replaced with slow-acting poisons such as hexaflumuron.
Bait Boxes
The principle of baiting techniques is to have a susceptible substance in an aggregation device
(bait station) on which the termites aggregate and continue to feed once they have found the
bait stations. Bait stations can be placed in in-ground and aboveground situations. A bait
toxicant in timber or a cellulose matrix can be placed in the station or dusting the termites
may indirectly destroy the colony. Colony elimination or suppression should be followed by
hazard reduction and regular inspection.
In Australia the main problem with baiting against Coptotermes species has been
inconsistency of termites locating and accepting baits. The method relies on termites finding
bait stations, which often does not occur. Baiting is most beneficial when used as part of an
integrated pest-management strategy. Bait stations buried in the soil might be found by
foraging termites (e.g. CSIRO’s bait box technique). Aboveground bait stations are placed in
direct contact with infested timbers where possible, and aggregation stations (plastic lunch
27
boxes containing bait) have been used successfully when placed in the hollow centres of
infested trees or stumps. The advantages of using baiting as part of an integrated pestmanagement strategy are that they do not lead to widespread contamination of the soil, and
require only a small amount of toxicant as opposed to other treatment systems which employ
a saturation approach. Baits may be used via a “bait and switch” technique in which the
original non-toxic bait used to aggregate termites is replaced by toxic bait. Alternatively, the
aggregated termites may be poisoned by topical application of a pesticide (i.e. arsenic dust
which is then carried back to the nest) or the baits may be toxic or contain metabolic, growth,
moult or chitin inhibitors. In all cases, the toxin must be slow-acting to allow termites to feed
and then move away from the bait and spread through the colony, as the presence of dead
individuals can have a repellent effect.
Example product: Sentricon (Dow Agrosciences). This is a monitoring and elimination
system. When termites are found in the station, the wood is replaced with a tube containing
bait toxicant. When termite activity ceases, the wood is returned to the bait station and
monitoring resumed. The active ingredient in the bait is hexaflumuron, a chitin synthesis
inhibitor (Recruit II). It is not suitable for low areas that may flood, as it is highly toxic to
aquatic invertebrates and possibly fish.
Dusting
If termite colonies are accessible, they may be directly dusted using arsenic trioxide or
permethrin dust, or alternatively aggregated individuals may be dusted so that they return the
poison dust to the colony. This is the favoured method of spot treatment of wooden railway
bridges and isolated and obvious nests.
Heat
o
o
In laboratory studies, increasing wood core temperatures to 46 C and 49 C resulted in 100%
mortality of C. brevis nymphs (Woodrow and Grace, 1998). However, this was in small
wooden blocks (13.5 x 13.5 cm). In larger wooden blocks where temperatures took longer to
rise, termites were better able to tolerate the conditions, and it has been hypothesised that
slow rates of thermal increase may lead to heat acclimation of termites. Cumulative effects of
sublethal stresses due to gradual heating may increase mortality. Heat treatments can be used
in whole-of building treatments by using a propane heating unit to blow hot air into the
building which is sealed within a tent of tarpaulins or similar. Hot air is blown in and around
o
the building to heat interior and exterior walls and temperatures must be maintained at 45 C
o
to 50 C for 50 minutes to an hour. This practice is rarely used.
Freezing
This is a method that is not practical for infestations of buildings, but can be used for specific
areas such as verandas and/or furniture. Liquid nitrogen is pumped into the sealed area to cool
o
the area to –20 C.
Electricity
Electricity has been used to spot-treat infested wood using an electrogun to deliver a low
current and high voltage, which kills the termites in its path.
28
Microwaves
Heat generated by microwaves can be used to kill termites. M icrowave generators are
mounted against the infested wall. M icrowaves can be used to treat wood as a preventative
measure. By passing wood through microwaves a change in structure may result. The
palatability of the wood to termites can be changed this way. The addition of pesticides and/or
preservatives in the early stages of the procedure is possible.
Radioactive isotopes
Techniques developed for tracing the movements of subterranean termites by feeding them
radioisotopes could potentially be used to exterminate colonies. Isotopes fed to termites via
insertion of a wooden dowel with an agar mixture of inert radioisotopes La-140 or Sc-45 were
spread through the colony over 24 hours (Airey and Charlton, 1994), thus demonstrating the
effectiveness of such a method. This technique poses technical and safety issues that render it
unsuitable for general use.
Carbon dioxide
Carbon dioxide may be a viable alternative to conventional pesticides in some situations such
as vault fumigation, and possibly for eradication of pests in structures. Significant mortality
has been recorded for C. formosanus exposed to 95% or greater carbon dioxide atmospheres.
However, 60 hours of exposure were required to produce 100% mortality (Delate et al.,
1995a).
Plant extracts
The fruits, seeds and leaves of the plant Melia azedarach Linn have been investigated in
Taiwan as an antitermite compound. When fed powdered fruits, leaves, bark and seeds
termites suffered 100%, 90%, 85% and 67.5% mortality respectively (Lin and Wang, 1988).
The oil from Neem trees, Azadirachta indica has antifeedant affects on Reticulitermes
speratus Kolbe. Extracts from Neem oil have been evaluated for their potential in termite
management (Isheda et al., 1992).
Termite resistant wood
Black cypress pine – Callitris endlicher i (and its latex) is resistant to termite attack. It grows
south of Kingaroy and west of the Great Dividing Range in Queensland. It is durable, and also
resistant to fungi. However, it is unpopular with builders because it is difficult to work with
and is often knotty. Long-term use will depend on the timber being grown in commercial
plantations. Some other Australian natives are described as “termite resistant”, with AS3360.2
(2000) listing 37 eucalypt, 9 non-eucalypt and 5 softwood species as suitable for minor
construction purposes such as fencing and landscaping.
Protozoicides
Several protozoicides have been investigated for use as baits. Waller (1996) investigated urea,
ampicillin and tetracycline fed to R. flavipes and R. viginica (Banks). The most effective of
these was urea, which was palatable and decreased termite survivorship.
29
Physical barriers
Sand, (12-grit) layered around the foundations of a house may act as a barrier against termites
(Ebling and Forbes, 1988). Basalt barriers with 50% or more of the particles with diameters of
1.7–2.8 mm was not penetrated by formosan subterranean termites in laboratory and field
trials (Tamashiro et al., 1991). Similarly, granite barriers were effective in some cases, for
some species. Verkerk (1990), states that gravel barriers are an effective barrier against
termites. A double barrier system, with a plastic membrane separating two different size
gravels would have to be used North of the Tropic of Capricorn due to the presence of M.
darwiniensis.
Deltamethrin impregnated blankets (e.g. Kordon Blanket, Bayer Cropscience) may be a
barrier against infestation, but any cracks, deformities or degeneration in the materials may
allow termites access.
S tainless steel mesh (e.g. Termimesh) can provide an effective barrier against infestation,
but any cracks, deformities or degeneration in the materials may allow termites access. Water
easily passes through this product. One of the major concerns with the use of Termimesh is its
positioning in relation to weepholes and external paths. In many cases external paths are built
above the level of existing weepholes.
Aluminium termite barriers, flashing and damp-poof coursing (e.g. Alterm). The Alterm
system is a combination monitoring and barrier systems. Baits are placed at the perimeter of
the structure in brick mortar joints, and if termite activity is detected, the baits are replaced
with toxins.
For subterranean cables, there are a number of barriers that are used, or have been
investigated for use, to prevent termites from damaging them. Welded stainless steel tubes are
used for high voltage cables to provide an effective termite barrier. The stainless steel tubes
are corrugated so that they are able to flex and bend to some degree without cracking. Power
and utility cables can be taped, with either stainless steel, brass or copper tapes, in an
overlapping fashion to form a seal that is impervious to termites. These cables are then
usually finished with a PVC coating for extra protection. High Density Polyethylene (HDPE)
cables are resistant to termite attack because they are too hard for termites to penetrate, are
smooth and therefore are difficult for termites to grasp with their mandibles.
Nylon is an effective termite barrier, used extensively to protect telecommunication cables.
As with HDPE, the effectiveness of nylon is as a result of its smooth impermeable surface.
Termite detection devices
M onitoring and detection devices are potentially useful for finding the location of an
infestation in a building. Borescopes are inserted into wall cavities to visually inspect for
termites. Termatrac (Protec USA) electronically emits signals that penetrate walls; insect
movement behind and within walls is detected by interrupted signals.
30
14. Future directions
The future of termite management lies within an integrated approach that is able to take into
account preventative and retrospective treatments for termites and that is not only effective,
but is also economical, safe and environmentally friendly. Such treatments are likely to
consist of physical and chemical barriers, used in combination with resistant or preserved
wood or steel framing and according to the requirements of individual sites.
For an integrated approach to be effective it must involve industry, government and consumer
groups and combine treatment and prevention programs with education, monitoring and
collating data, and research into new and better measures for termite management. There is a
widely perceived need for improvements in building design in order to prevent or reduce
termite infestation along with increased interest and demand for physical barrier systems.
New building techniques and designs, along with novel barrier systems to reduce exposure to
termites are warranted, and further research on termite foraging behaviour is required to
facilitate the development of more effective bait and monitoring technology.
Currently in Australia, we may be enjoying a period of overlap where older buildings are still
being protected by the organochlorines while new structures are treated with
organophosphates. Houses built before 1985 may still be protected to some extent by the
organochlorine termiticides applied to them. However, the effectiveness of the residual
organochlorines will have been reducing over time, and older houses may be at risk of termite
infestation. The potential costs of re-treatment and repairs are likely to increase dramatically
in the future as older slab-on-ground dwellings become susceptible due to the eventual failure
of the organochlorine termiticides.
The success of the organochlorines over long periods of time has added to the popularity of
slab-on-ground housing in Australia, buildings which are much more susceptible to
infestation by termites than older style above-ground housing. This means that the potential
for termite damage is increased. The result of Australia’s previous reliance on the highly
persistent organochlorines is that modern housing is quite susceptible to attack by termites,
with termites entering buildings through weepholes, expansion joints, service ducts and
cracks in brickwork which often extend several courses below ground. Simple alterations in
building and property maintenance practices, such as providing exposed slab edges above
ground and extending aprons of slab around slab-on-ground dwellings will allow termite
incursions to be reduced and detected, providing that regular inspections take place.
There are many areas in which the efficiency of different pesticide formulations needs
investigating. Therein lies the potential for chemical companies to examine their formulations
to suit specialised purposes. There are many areas in which different management techniques
can be investigated, the electricity supply industry being an example. In Australia, there are
approximately 8,000,000 wooden power poles, which are inspected (typically at 5-year
intervals) for termite infestation and rot. These poles exist in a wide range of conditions, in
urban and rural environments, in a range of soil types and climates, some adjacent to
waterways or drainage areas. However, despite these substantial differences in circumstance,
31
all are treated by similar processes using commercial formulations where termiticides are
applied. Biflex (bifenthrin) is most commonly used on wooden poles today. Previous
treatment regimes included chemicals such as aldrin, creosote and chlorpyrifos treatments.
M any wooden poles are fluoride treated to prevent rot and most wooden poles are now CCA
pre-treated. Issues with current treatment include concerns about the uncertain potential of the
chemical “cocktail” of treatments around each power pole.
There are 54.5 km of timber railway bridges in Queensland alone and approximately 9500 km
of rail corridor. Each bridge is susceptible to termite attack and undergoes inspection every 4
to 8 years. Treatment is on discovery of termite activity and is by arsenic dusting into nests
and application of chlorpyrifos or bifenthrin to soil. Other chemicals sometimes used are
fipronil and imidacloprid. Over the last 10 years, 40 km of timber bridges have been replaced
with concrete structures, particularly those in tropical regions. However, many timber bridges
are likely to remain. Construction of concrete footing to keep timber supports from contacting
the ground is being considered as a means of reducing termite damage.
There is potential for clients to work with termite managers and chemical companies to
review their formulations to suit their specialised purposes, identify termite management
strategies appropriate to the location of infrastructure, and potentially to develop chemicalfree physical barriers and/or more sustainable termite management practices. Future
approaches based on integrated pest management principles require the cooperation of
stakeholders in order to gather information and perform research into the problem in a holistic
fashion.
Several requirements are apparent:
•
M ore information is required on Australian termite biology, taxonomy and ecology.
Ideally, an understanding of the way in which termites forage, how they locate food
sources, what specifically attracts and repels them, and the mode and speed of
infestations need to be gained.
•
The risks of termite infestation need to be evaluated, both locally and nationally so
that susceptible or high-risk areas, structures and building types can be identified and
preventive measures taken in terms of design and construction. Building regulations
and designs need to be able to reduce or eliminate high-risk housing – and eliminate or
reduce conditions that are attractive to termites and/or facilitate termite infestation.
•
Further education is required for homeowners, builders, designers, legislators and
landscape designers so that they can reduce the risk of infestation through the
avoidance of practices in landscaping and design that inadvertently favour termites i.e.
ensuring good under-floor ventilation, which discourages termite activity, not stacking
timber or building up soil against or near buildings, reducing timber use where
inspection for termites is difficult, and not building wooden in-ground structures (e.g.
untreated timber retaining walls) close to houses.
•
There needs to be a specific focus on the creation of alternative barriers for the range
of wooden structures that need protection. The focus needs to take account of the
current limitations of physical barriers and monitoring stations which may be avoided
32
by termites and overcome the loss of activity associated with short-term response
chemicals which have replaced the more hazardous organochlorine compounds. An
innovative approach to barrier design is needed that seeks to incorporate the specific
features of slow release chemicals, e.g. based on natural products which are more
acceptable to the environment and public health.
•
Since most termite-related damage to timber occurs from subterranean termites,
preventative measures rely heavily on site housekeeping and the establishment of
physical or chemical barriers to stop the termites getting into the premises or timber
from the underlying soil. Once the termites have been found in wooden structures, a
range of physical and chemical techniques are available to treat and eliminate (or
control) the infestation. There is a need for a reliable long-term, maintenance-free
method of preventing termite infestations that poses little or no risk to human or
environmental health.
Research is required into the behaviour of termiticides, current and potential, in Australian
soils and under Australian conditions using rigorous, repeatable science, and open and
collaborative communication between stakeholders needs to be maintained and widened so
that the concerns of each group are addressed.
33
Recommended further reading
AS 1604.1 (2000). Specification for preservative treatment – Part 1: Sawn and round timber.
(Standards Australia, Sydney).
AS 3660.1 (2000). Termite management – Part 1: New building work. Standards Australia,
Sydney.
AS 3660.2 (2000). Termite management – Part 2: In and around existing buildings and
structures - Guidelines. Standards Australia, Sydney.
AS 3660.3 (2000). Termite management – Part 3: Assessment criteria for termite management
systems. Standards Australia, Sydney.
AS 3660 (1993) Australian Standard relating to termite protection for existing buildings
Protection of Buildings from Subterranean Termites – Prevention, Detection and Treatment of
Infestation Standards Australia, Sydney. This standard was partially superseded by AS 3660.1
(1995).
AS 3660 Supplements for use by Pest Control Operators: Standards Australia, Sydney.
Supplement 1 (1993): Certification of Termiticide Application.
Supplement 2 (1993): Certification of Completion of Treatment.
Barron, M.G. and Woodburn, K.B. (1995). Ecotoxicology of chlorpyrifos. In Ware, G.W.
(ed.). Reviews of environmental contamination and toxicology pp. 1-94. Volume 144.
Continuation of residue reviews. Springer Verlag. New York Inc. U SA.
Bloomquist, J.R. (1999). Insecticides: Chemistries and Characteristics. In E.B. Radcliffe and
W.D. Hutchison (eds.), Radcliffe’s IPM World Textbook, URL: http://ipmworld.umn.edu
University of M innesota, St. Paul, M N.
International Programme on Chemical Safety (IPCS ). Chemical Safety Information
from Intergovernmental Organizations. Website: http://www.inchem.org
International Programme on Chemical Safety (IPCS ). Pesticide Data Sheets.
http://www.inchem.org/pages/pds.html
International Programme on Chemical Safety (IPCS ). Environmental Health Criteria 18 –
Arsenic. Website: http://www.inchem.org/documents/ehc/ehc/ehc018.htm
International Programme on Chemical Safety (IPCS ). Environmental Health Criteria 97 –
Deltamethrin. Website: http://www.inchem.org/documents/ehc/ehc/ehc97.htm
International Programme on Chemical Safety (IPCS ). Environmental Health Criteria 142
– Alpha-cypermethrin. Website: http://www.inchem.org/documents/ehc/ehc/ehc142.htm
International Programme on Chemical Safety (IPCS ). Environmental Health Criteria 204
– Boron.Website: http://www.inchem.org/documents/ehc/ehc/ehc204.htm
34
International Programme on Chemical Safety (IPCS ). Health and Safety Guide No. 39 –
M irex. Website: http://www.inchem.org/documents/hsg/hsg/hsg039.htm
International Programme on Chemical Safety (IPCS ). Health and Safety Guide No. 86 –
M ethyl Bromide. Website: http://www.inchem.org/documents/hsg/hs g/hs g86_e.htm
Kookana, R.S ., Baskaran, S . and Naidu, R. (1998). Pesticide fate and behaviour in
Australian soils in relation to contamination and management of soil and water: a review.
Aust. J. Soil Res. 36: 715–764.
Lenz, M., Watson, J.A.L. and Barrett, R.A. (1988). Australian efficacy data for chemicals
used in soil barriers against subterranean termites. CSIRO Division of Entomology Technical
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National Registration Authority (2000). The NRA review of chlorpyrifos. NRA review
series 00.5. National Registration Authority for Agricultural and Veterinary Chemicals.
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Racke, K.D. (1993) Environmental fate of chlorpyrifos. In Ware, G.W. (ed.). Reviews of
environmental contamination and toxicology. pp. 1 – 151. Volume 131. Continuation of
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Therapeutic Goods Administration (2001). Termite Protection: Available Treatments and
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Committee and the FQPA Safety Factor Committee, Health Effects Division. Office of
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Ware, G.W. (1999). An introduction to insecticides (3rd edition). In E.B. Radcliffe and
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Ware, G.W. (ed.) (1995). Reviews of environmental contamination and toxicology. Volume
144. Continuation of residue reviews. Springer Verlag. New York Inc. U SA.
35
Warne, S .J., Westbury, A-M. and S underam, R.I.M. (1998). A compilation of data on the
toxicity of chemicals to species in Australasia. Part 1: Pesticides. Aust. J. Ecotoxicol. 4: 93144.
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43
Index
Acceptable Daily Intake (ADI), 20
AchE inhibition, 24
Acute Reference Dose (ARD), 20
adjuvants, 19
aldrin, 7, 17, 20, 38
Alpha-cypermethrin, 12, 13, 22, 26
alternative treatments, 33
aquatic systems, 24
arsenic trioxide, 7, 17, 22, 34
Aspergillus niger, 33
Azadirachta indica, 35
bait stations, 17, 34
barriers, 1, 2, 3, 4, 6, 11, 32, 33, 35, 36
Beauvaria bassiana, 32, 33
bees, 23, 24, 28
benzoylurea, 17
Bifenthrin, 4, 7,11–13, 19, 22, 25, 26
biological control, 32
boron, 7, 17
C. acinaciformis, 17
cables, 36
carbon dioxide, 35
carcinogenic effects, vi, 31
castes (termite), 5, 6
chlordane, 7, 20
chloronicotinyls, 7, 14
Chlorpyrifos, 3, 4, 6, 7, 10, 11, 18–23, 26–31, 38
copper, 7, 17, 26
Coptotermes acinaciformis, 5
Coptotermes acinaciformis raffrayi, 5
Coptotermes lacteus, 6
Coptotermes michaelseni, 5
Cornitermes cumulans, 6
costs, 1, 3, 37
creosote, 7, 17, 37
cyclodienes, 7
cypress pine, 36
Daphnia, 28
degradation, 10, 13, 18, 19
Deltamethrin, 14, 22, 27–31, 36
dieldrin, 7, 20
drywood termites, 4, 5, 7, 17
dusting, 6, 7, 17, 33, 34, 38
dusts, 6, 17, 19
earthworms, 23, 24, 25
efficacy, 6, 18, 19, 20
electricity, 34, 37
44
entomopathic fungi, 32
EPA, 21, 26
experimental LD50 and LC50 values, 26
fate in humans and animals, 32
Fipronil, 4, 7, 16, 22, 23, 25, 26, 27, 28, 30, 31, 38
fluorine, 7
foraging, 1, 6, 33, 34, 37
formulations, 4, 7, 10, 14, 17, 18, 19, 20, 24, 38, 39
freezing, 34
fungi, 32, 33, 35
GABA, 11, 16
golden orfe, 28
grooming, 6, 33
groundwater, 13, 15, 18, 19, 22, 25
growth inhibitors, 17
heat, 35
heptachlor, 7, 20
Hexaflumuron, 17, 22, 25
high density polyethylene, 36
humans, 7, 10, 20, 21, 22, 23, 32
Imidacloprid, 4, 7, 14, 15,18, 22, 24, 26, 28, 29, 30, 31, 32, 38
impregnated wood preservatives, 17
incidents, 26
Introduction, 4
invertebrates, 23, 24, 34
Iridomyrmex glaber, 32
isofenphos, 19
Japanese quail, 27
Kalotermitidae, 5
Koc , 10, 11, 12, 13, 15, 16
Kordon, 14, 36
Kow, 12, 13, 14, 15, 16
landscaping, 1, 35, 38
LD50, 21, 23, 24, 26, 28
Log Kow, 10, 11, 12, 15, 16
Mastotermes darwiniensis, 5, 7, 17, 36
M astotermitidae, 5
Melia azedarach, 36
Metarhizium anisopliae, 32, 33
methyl bromide, 7, 17
microwaves, 35
M irant, 7, 17
M irex, 7, 17
monitoring and baiting, 33
monoterpenoids, 32
mutagenic effects, vi, 31
Neem oil, 36
nicotinoids, 14
NRA, 4, 20
nylon, 36
45
organic content, 11, 18
organochlorines, 1, 7, 17, 38
organophosphates, 1, 7, 18, 19, 21, 37
oysters, 26
Permethrin, 4, 7, 11, 17, 19, 22, 26, 28, 28, 30, 31, 32, 35
persistence, 7, 18, 19, 20, 23
phenyl pyrazoles, 7, 16
plant extracts, 35
power poles, 4, 20, 37
predators, 32
protozoicides, 35
PVC coating, 36
pyrethrins, 11
pyrethroids, 7, 11, 12, 13, 19, 22, 24
radioactive isotopes, 35
railway bridges, 34, 38
reproductive effects, vi, 30
resistant wood, 36
Rhinotermitidae, 5
runoff, 23, 26
Schedorhinotermes reticulatus, 5
semiochemicals, 32
Silafluofen, 32
solubility in water, 10, 11, 12, 13, 14, 15, 16
solvents, 3, 10, 12, 19, 20, 26
sorption, 10, 11, 12, 15, 16
sorption coefficient, 10, 11, 12, 15, 16
spills, 23
tap water, 26
teratogenic effects, vi, 30
Termimesh, 36
termite fauna, 5
Termitidae, 5
Termopsidae, 5
toxicity tests, 20, 22
Triflumuron, 17
tunnelling (termites), 6
volatilisation, 10, 11, 18
waterfowl, 25
wildlife, 24, 25
wood preservatives, 7, 12, 17
46

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