Plant based, eco-friendly wood preservatives for termite control

Plant based, eco-friendly wood preservatives for termite control
Track/Theme: Sustainable consumption, consumer responses and new markets for ecoproducts OR Climate Change and energy
VERMA Monica*, SHARMA Satyawati and PRASAD Rajendra
Centre for Rural Development and Technology
Indian Institute of Technology Delhi
Hauz Khas, New Delhi – 1100016
E-mail: monica24_iitd@yahoo.com
* Main author and presenter
Abstract
Termites are the most troublesome pest of agricultural crops and wooden structures,
causing billions of dollar damage annually through out the world. Most popular and
widely used prevention measure to reduce the infestation of termites is the use of
synthetic termiticides. These are very harmful chemicals. Several termiticides are
registered for termite control across the world under various brand names like spinosad,
disodium octaborate tetrahydrate (DOT), calcium arsenate and chlorpyriphos. Although,
chemical control is an effective measure of protection by termites but their excessive use
is harmful for our environment and the results are not sustainable. Many researchers are
trying to develop new methods of termite control. Plant derived natural products,
entomopathogenic fungi, nematodes and bacteria are some of the alternative methods of
termite control. Some plant biomass contains insecticidal activity which can be exploited
for termite control. Present paper deals with field level results of work done at
micromodel CRDT, IIT Delhi on the efficacy of certain selected plant biomass in
controlling termites. 14 plants having insecticidal activity were procured from IIT Delhi
campus. They were screened for their termiticidal activity. A chemical, chlorpyriphos
was also used for comparisons. Out of 14, 5 botanicals were found to be effective against
termites. Although some botanicals were not as effective as chemical but they are
nontoxic and safe for the environment, biodegradable and renewable source. The plant
extract could be exploited to develop new wood preservatives to protect wooden
structures, agricultural crops, plants and trees, as these are less harmful to the
environment and humans. Further, studies are required to use them as commercial
termiticide.
Keywords: Termites, botanicals, termiticides, chlorpyriphos
1. INTRODUCTION
Termites are the most troublesome pest of plants, trees and wooden structures. They
severely damage agricultural crops and urban infrastructure. There are about 2,500
species of termites in the world and only 10% have pest status. Out of 300 species in
India, about 35 have been reported as damaging agricultural crops and timbers in
buildings. They cause over 3 billion dollars in damage to wooden structures annually
throughout the United States [8]. In India, they cause the yield loss of 15- 25% of maize
and about 1,478 million Rupees [7]. Termites can attack plants at any stage of
development from the seed to the mature plant. Crop losses and termite genera
responsible in different continent and different termite genera in subcontinent is
described in Table 1 and 2 respectively.
They are social insects that live together as a colony in a nest. Colony members
belong to one of three interdependent groups with specialised form and function known
as castes. The three basic castes present in the colony are workers, soldiers and
reproductive forms. Workers and soldiers are wingless, sterile and blind. Workers
construct the distinctive shelter tubes and collect food to feed the young and other
members of the colony. The primary function of the soldiers is to defend the colony,
usually against ants, which are their main enemies. The reproductive caste is usually
referred to as the king and queen. They are responsible for the production of fertilised
eggs for the colony and of specialized chemicals (hormones) important for managing the
inhabitants of the colony. Mature colonies produce winged reproductive forms or alates
at certain times of the year. After the dispersal flight, the alates attempt to find mates and
found new colonies [5]. Termites are most successful of all the social insects because
colony members are long lived and because they utilize cellulose as food source. They
depend entirely over wood, either living or dead, or the woody tissue of plants, intact or
partially decayed and also in the form of humus and dried animal dung.
Termites which belong to the following families and genera: Hodotermitidae
(Anacanthotermes and Hodotermes), Kalotermitidae (Neotermes), Rhinotermitidae
(Copotermes, Heterotermes, and Psammotermes), and Termitidae (Amitermes,
Ancistrotermes,
Cornitermes,
Macrotermes,
Microcerotermes,
Microtermes,
Odontotermes, Procornitermes, and Syntermes) cause great losses in agriculture [17].
Table 1. Crop losses and termite genera of different continents
Country
Africa
Crop
Groundnut
Maize
Sugarcane
Losses (%)
Termite species
Between 10 Microtermes and Odontotermes
and 30
30- 60
Microtermes, Ancistrotermes Macrotermes spp.
Odontotermes,
Allodontermes,
and
5-10 (Central Pseudacanthotermes
Africa)
Amitermes, Pseudacanthotermes, Macrotermes,
18 (Sudan)
Odontotermes,
Microtermes
and
Ancistrotermes
Southeast
Asia
Sugarcane
12 (Pakistan)
Australia
Cashew, mango 30
and
avocado
trees
Microtermes, Coptotermes, Odontotermes,
Macrotermes, Trinevitermes and Heterotermes.
Mastotermes, Heterotermes, Coptotermes,
Amitermes and Microcerotermes
Source : www.chem.unep.ch/pops/termites
Table 2 : Important termite genera in subcontinents
Country
Southern
Africa
Important termite genera and species
Anacanthotermes (Family Hodotermitidae), Psammotermes and
Reticulitermes
(Family
Rhinotermitidae),
Amitermes,
and
Microcerotermes (Family Termitidae), and several species of
Kalotermitidae
Eastern
Macrotermitidae: Macrotermes (Family Termitidae), Hodotermes (Family
Africa
Hodotermitidae), and Schedorhinotermes (Family Rhinotermitidae).
Western
Ancistrotermes, Macrotermes, Odontotermes, Microtermes, and
Africa
Cubitermes(Termitidae).
N. America Dampwood termites: (genus Zootermopsis, Family Termopsidae)
Drywood termites: (Incisitermes, Neotermes
Subterranean termites (Reticulitermes, Heterotermes, Amitermes, and
introduced species of Coptotermes
S. America Cryptotermes and Neotermes (Family Kalotermitidae), Coptotermes and
Heterotermes (Family Rhinotermitidae), and Nasutitermes
China
Coptotermes, Reticulitermes (Family Rhinotermitidae), Macrotermes and
Odontotermes members of the Cryptotermes (Kalotermitidae) and
Hodotermitidae
Australia
Subterranean, drywood, harvester, and mound builders Mastotermes,
porotemes, stolotemes (primitive genera)
Europe
Reticulitermes
Source: www.chem.unep.ch/pops/termites
Control measures
A number of control measures are used to prevent termite attack on buildings as well
as on crops. These are physical, chemical and biological.
Physical
Physical method of control includes physical barriers and treatment. Barriers are of
two types: non toxic and toxic. Non toxic physical barriers are substances (e.g., sand or
gravel aggregates, metal mesh or sheeting) that exclude termites through the impenetrable
material act as a physical/mechanical barrier to prevent termite penetration and damage to
building and toxic chemical barrier includes the use of chemical termiticides in soil
around the building and creation of a zone of poisoned soil under and around the
structure to prevent termites entering from the ground [3]. Treatments consist of heat,
freezing, electricity and microwaves.
Chemical
It is the most important and most widely used prevention measure to reduce the
infestation of termites. Several termiticides are registered for termite control across the
world under various brand names. They contain the following active ingredients:
bifenthrin, chlorfenapyr, cypermethrin, fipronil, imidacloprid and permethrin. Various
chemicals spinosad, disodium octaborate tetrahydrate (DOT), calcium arsenate and
chlorpyriphos are also used. The chemical toxicity, formulation and application method,
as well as dry wood termite behavior and gallery system, architecture influenced the
performance of local chemical treatment [14]. Chemical Treatments comprises
groomable coating, soil termiticide injection, baits and chemical fumigation [6].
Chromated copper arsenate (CCA) treated southern yellow pine and radiata pine was
found to be toxic against formosan subterranean termites, Coptotermes formosanus [4].
Soil termiticide injection, used for subterranean termites. It includes drilling of the
foundation wall/slab, injection of termiticide from below slab and in the soil in contact
with foundation. Plugging drill holes on interior with cement, or caulking [6].
Chemical Fumigation usually used for drywood termite infestation. This strategy is
employed to deal with drywood termites, aerial colonies of subterranean termites and
cases where arboreal species nest inside structures. It includes the use of toxic gas inside
the structure. Removal of all chemical absorbent materials from the building to be
fumigated. Tenting of whole building and evacuation of surrounding properties followed
by pumping in of fumigant and allowing time to penetrate the wood finally venting of gas
and removal of tent [6]. These gases must be used with extreme care, because they are
extremely toxic to humans, as well as other animals, and plants. Improper or careless use
can result in death or injury. Fumigants treat all termite infestations or colonies
simultaneously, and have high levels of efficacy, if correctly applied. Active ingredient in
various fumigants are Carbon Dioxide (Asphyxiant), Methyl bromide, Phosphine,
Sulfuryl fluoride (Metabolic poison). Methyl bromide is a commonly used fumigant [17].
Baiting is an environmentally sound method of termite control. It uses very small
amount of insect toxicants. Baits can be toxic or nontoxic. Bait technology uses wood or
a cellulose matrix favored by termites that is impregnated with a slow-acting toxic
chemical. The workers were exposed to lethal dose of desirable food bait. Bait station is
placed into soil at intervals around building, baits inside contains slow-acting chemical.
Termite workers feed upon the bait and transfer it by grooming or trophallaxis (licking)
to other colony members, thereby reducing or eliminating the entire colony. Bait
consumption by termite depends on bait design [2]. Termites are not site-specific, but
rather, they forage among various food sites, which results in the bait being encountered
by many colony members. The toxicant necessarily is slow acting because termites tend
to avoid sites where sick and dead termites accumulate. Successful termite baiting
necessitates proper monitoring and maintenance of the stations. Baits are often used in
sensitive environments. A number of baits have been marketed to control termites. The
bait product contains the following ingredients: diflubenzuron, hexaflumuron,
sulfluramid and noviflumuron. Among them hexaflumuron is the most popular bait
toxicant (Table 4).
Table 4. Different bait toxicant, their mode of action and application
Active Ingredient
Mode of Action
Application/
Considerations
Diflubenzuron
Chlorflurazuron
Hexaflumuron
Triflumuron
Disodium octoborate
Chitin synthesis inhibitor
Chitin synthesis inhibitor
Chitin synthesis inhibitor
Chitin synthesis inhibitor
Metabolic toxin
In food matrix
In food matrix
In food matrix
Dust
In food matrix/dust
tetrahydrate
Arsenic trioxide
Hydramethylnon
Sulfluramid
Biocontrol Agents
Fungus:
spores,
mycelium.
Nematodes:
stages
Metabolic toxin
Metabolic inhibitor
Metabolic Inhibitor
Dust
In food matrix
In food matrix
Grows through cuticle andUse as bait and soil
utilizes entire termite body
treatment
is experimental.
infective Invade; carry bacterium which Bait system is experimental
produces lethal toxins
Source: www.chem.unep.ch/pops/termites
Biological control
Alternative means for pest control should be searched to minimize the use of synthetic
chemicals. The use of botanicals and biocontrol agents are a promising alternative to
chemical control. Botanical pesticides possess an array of properties including
insecticidal activity, repellency to pests, antifeedency, insect growth regulation, toxicity
to agricultural pests [9, 10, 11, 12, 13]. Plant derived natural products, entomopathogenic
fungi, nematodes and bacteria are some of the alternative methods of termite control.
Nematodes caused high mortality of Reticulitermes flavipes (Kollar) termites in
laboratory tests [16]. The entomopathogenic fungi play significant role in integrated pest
management [1]. Beauveria bassiana (Balsamo) Vuillemin has been shown to be highly
pathogenic to many insect species in both temperate and tropical regions [15]. A fungus
Metarhyzium aniospliae (Bio Blast) is another biological termiticide that require special
application and handling technique.
2. METHODOLOGY
2.1 Plant materials
Leafy biomass of 14 plants (Asafoetida, Azadirachta indica, Calotropis gigantea,
Cannabis sativus, Curcuma amada, Datura alba, Eucalyptus globulus, Jatropha curcus,
Lantana camara, Musa paradisiaca, Pongamia pinnata, Parthenium hysterophorus,
Ricinus communis and Tagetus erecta) was collected from Indian Institute of Technology
Delhi, campus. Hot water extracts of 10% concentration were prepared by boiling 100gm
of the selected plant biomass in 1 liter of distilled water for 1 hour then left it for further
extraction. Thereafter, it was decanted and filtered with Whatman filter paper. A
pesticide chlorpyriphos (O,q O–diethyl O -3, 5, 6- trichlor-, O - 2pyridylphosphorothioate) was also used for comparisons.
2.2 Termite test
Wooden blocks of kail wood (Pinus excelsa) of size (26 x 4 x 1 cm3) were dried in the
oven at 60 o C overnight and weighed. Before treatment, all test blocks were conditioned
at 27o C and 70% relative humidity (RH) for two weeks. They were dip-treated with plant
extracts overnight in plastic trays. The extract and chemical treated blocks were air-dried
and inserted into termite infested area in IIT campus. The blocks were observed daily.
2.3 Mass loss analysis
After four weeks period, the blocks were removed, cleaned, dried overnight and weighed
to determine weight loss. Loss in weight of blocks was recorded as percent mass loss.
3. RESULTS AND DISCUSSION
Termite test
Wood consumption (as per mean % weight loss) of extract treated and untreated blocks
by O. obesus are given in Table 1. Aqueous extract of Cannabis sativus leaves caused
significant protection with 4.94% of P. excelsa wood loss against Odontotermes obesus.
Similarly, extracts of Datura alba fruits, leaves of Curcuma amada, Asafoetida and
Ricinus communis provided effective protection with 10.50, 11.19, 11.28 and 16.33 %
wood weight loss respectively. Therefore, these treatments are effective against
biodeterioration of wood by O. obesus. The chlorpyriphos treated wooden blocked was
unattacked by termites through out the test period. The control blocks were completely
consumed by termites as there was no barrier of any protective coating around them. This
suggests that though chemical are an effective control against termites but they are
harmful too. Therefore, search of alternatives control measures is essential. These
botanicals can be used in combination with chemical pesticide to lower their harmful
effect.
Table 1. Percentage weight loss of wood blocks treated with 10% concentration of
various Leaf extracts.
Treatment
Mean weight loss (%)
(Mean ± SD)
Asafoetida
Azadirachta indica
Calotropis gigantea
Cannabis sativus
Curcuma amada
Datura alba
Eucalyptus globulus
Jatropha curcus
Lantana camara
Musa paradisiaca
Pongamia pinnata
Parthenium hysterophorus
Ricinus communis
11.28± 0.08
15.77± 2.66
48.43 ± 4.09
4.94 ± 1.61
11.19 ± 0.08
10.50 ± 6.27
49.07 ± 32.02
51.17 ± 5.95
45.13 ± 11.79
47.37 ± 4.32
48.40 ± 8.75
40.80 ± 6.70
16.33 ± 3.97
Tagetus erecta
Chlorpyriphos
Control
23.60 ± 3.54
0.00
100.00
4. CONCLUSION
In the present study the extracts of Cannabis sativus, Datura alba, Curcuma amada,
Ricinus communis and Asafoetida were found to be effective against termites. Although
some botanicals were not as effective as chemical but they are nontoxic and safe for the
environment, biodegradable and renewable source. The plant extract could be exploited
to develop new wood preservatives to protect wooden structures, agricultural crops,
plants and trees, as these are less harmful to the environment and humans. Further, short
and long term field studies are required to use them as commercial termiticide.
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[17] www.chem.unep.ch/pops/termites/termite_ch4.htm