What is Biological Control and Why is it Needed?

What is Biological Control and Why is it Needed?
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Read chs 1 and 2 of text
Goals of Biological Control
• Global invader suppression: Lower
density of invasive pest in the whole
landscape, permanently
• Help farmers: Keep pest density in crops
below injury levels, for one or more seasons
Target Groups
Usual targets
• Insects (whiteflies, aphids, mealybugs, weevils)
• Mites (2-spotted spider mite-via augmentation)
• Plants (waterhyacinth, Salvinia, thistles, spurge)
Rarely targets, but has been done
• Other invertebrates (snails, millipedes)
• Vertebrates (rabbits, cats)
Types of Natural Enemies
• Parasitoids
• Predators
• Pathogens (of both in insects, weeds,
vertebrates)
• Specialized herbivores
Techniques of Biological Control
Area wide, Field level
permanent control
control
Against insects
or weeds
XX
XX
I, W
Habitat manipulation
XX
I
Pathogens as pesticides
XX
I (W)
Insectary releases
XX
I
Classical biocontrol
Reasons BC is Needed
1. Invasions of new exotic pests
2. Problems with pesticides
Invasions of new exotic pests
INSPECTIONS TO SLOW RATE OF PEST INVASION
Invasions of new exotic pests
INCREASING LOAD OF INVASIVE PEST INSECTS
Invasions of new exotic pests
OVER HALF OF INVASIVE INSECTS BECOME PESTS
Problems with pesticides
MANY PESTS ARE RESISTANT TO PESTICIDES
A history of the development of resistance to pesticides by
Colorado potato beetle on Long Island, New York
lead arsenate
cryolite
flood
cryolite
pyrethrum
pyrethrum
sabadilla
flood
sabadilla
lead arsenate
nicotine sulphate/fish oil
Before 1945, pesticides were based on
minerals (e.g., lead, cryolite, arsenic)
and plant extracts (e.g., pyrethrum,
sabadilla, nicotine, etc)
DDT
dichloro-diphenyl-trichloroethane
Paul Hermann
Müller (1899 1965)
In 1939, the insecticidal properties of a synthetic chemical,
DDT, were discovered. The large scale use of DDT to delouse
soldiers and civilians in WWII spurred the creation of an
industry for chemical (rather than botanical) pesticides.
flood
DDT
DDT
DDT
flood
DDT
flood
flood
DDT
DDT
Lead arsenate
DDT
DDT
flood
Lead arsenate
DDT became
widely used
for most pests
The 1950s and 1960s were the era of
chemical pest control
This control system
1. Was based on rapid development of many new pesticides
2. Employed pesticides as the sole method of control
3. Used preventative and calendar based applications
4. Treated at the first sign of pests in crop, regardless of number
5. Did not monitor to learn current pest density
6. Was inexpensive and effective but polluting and not sustainable
Problems with pesticides
USE OF PESTICIDES IN MAJOR CROPS
Reasons for the End
of the Chemical Pest Control Era
1. Pest control failures due to pesticide resistance
2. Pest outbreaks due to resurgence
3. Pest outbreaks due to secondary pests
4. Environmental contamination with residues
Pest Resurgence
Natural Enemy (3)
www.uky.edu/Classes/ENT/530/Lecture_Notes/ mar29/mar29.ppt
Pesticide is applied
Pest = 2
Natural Enemy = 0
Pest = 7
Natural Enemy = 3
Pest = 14
Problems with pesticides:
Pest control failures due to the destruction of natural enemies
(pest resurgence or secondary pest outbreaks)
DeBach demonstrated resurgence by using DDT to eliminate Aphytis
melinus from citrus groves. Red scale populations exploded
Pesticide applied to kill target pest
Secondary Pest
Outbreak
Target pest
natural enemy of
secondary pest
secondary pest
In the absence of its natural enemies, the
“secondary pest” rapidly increases in density
Outbreaks of two
spotted spider mites
are routinely caused
when pesticides
applied for other pests
kill most of the
phytoseiid predator
mites that normally
control spider mites
Pesticides also damaged the
environment
Influential book
sounding alarm over
pesticide abuse
Pesticides in food chains
Bioaccumulation refers to
the concentration in a
food chain of a fat soluble
material such as DDT or
PCB. This lead to loss of
eagle and falcon
populations in wide areas
Thin-egg-shell syndrome in raptors, pelicans and other wading birds
Illness in farmworkers exposed to fresh pesticide residues
use new
pesticide
Pesticide
Treadmill
resistance
use more
pesticide
START:
Pest
Problem
chronic
outbreaks
use more
pesticide
resurgence &
replacement
use
pesticide
www.agls.uidaho.edu/hort_disease/ Lectures/Lecture02_IPM.ppt
Shift to IPM
In the 1960s,
pesticide use
dominated pest
management.
IPM was invented
as process to
reinsert natural
enemies into the
control system
Critical paper: Stern,
Smith, Hagen and
van den Bosch,1959
“The Integrated
Control Concept”
Critical Project:
control of the spotted
alfalfa aphid
Robert van den Bosch was an outspoken critic of
pesticide misuse
To monitor mites in
apples, for
example, one has to
count the mites on
samples of leaves,
frequently (1 or 2
times per week)
Counting mites
Traps can be used to track
relative abundance of pests in
crops
White traps for
apple sawflies
Yellow traps for whiteflies
Red ball
traps for
apple
maggot
flies
SPRAY
DO NOT SPRAY
Infestation Level
Pest injury levels indicate what density of pests really cause losses
spray
Economic
Injury Level
Economic
Threshold
with
control
May
June
July
August
Deformed frogs:
An unsolved
problem
Caused by
herbicides?
Looking back: how did use of
biological control get started?
Before use came
knowledge, beginning
with understanding of
the existence and
biology of natural
enemies. Predators
were obvious, but
parasitoids and
pathogens were first
understood in the 18th
and 19th centuries, in
Europe
parasitioids
1662 WOODCUT IN EUROPE
#1. Precedent for classical biological insect control:
Vedalia beetle, in CA, controlled cottony cushion scale
and saved an young but important industry
To import
predators into CA
from the native
range of cottony
cushion scale
(Australia)
required long ship
journeys, which
required rearing
the insects
through several
generations on
board
OVER HALF OF INVASIVE INSECTS
BECOME PESTS
Cryptochetum iceryae also was an important but less
visible natural enemy of cottony cushion scale
Data showing control of CCS in Australia on caged and uncaged
plants- caging raises scale survival from 5 to 50% (Prasad 1989)
Data showing that source of control of CCS in Australia varies by
season, with Rodolia being the key agent in warm periods and the fly
during cooler months (Prasad 1989)
Making a Science out of It
1.
2.
3.
4.
5.
6.
1913-hired to give direction to
BC efforts of Hort. Comm.,
which were drifting
Began to place use of BC on
scientific basis
Healed rift with USDA
allowing CA to continue to
import natural enemies
Served as head of BC efforts
from 1913 to 1951
Oversaw movement of BC
programs from state to
University in 1923
Trained first graduate
students in biological control
Paul DeBach
career: 1945-1983
1. Wrote 1964 basic text
for science
2. Solved the red scale
problem
3. Developed methods to
evaluation natural
enemy impacts
Paul DeBach
Control of a GWSS, Plant Disease Vector
Mark Hoddle
Glassy wing sharpshooter
Mark Hoddle and other worked to control glassy wing
sharp shooter, a threat to the wine industry. Control has
been achieved in CA, Tahiti, and other islands
More precedent projects
#2. Precedent for classical biological weed control:
Introduced moth controlled Opuntia cactus in Australia
Infestation in Australia in the 1920s before natural enemy release
Of 50 species considered, one (Cactoblastis cactorum) was
dramatically successful in reducing cactus density
After natural enemy release----collapsing, dying stands of cactus
OVER HALF OF INVASIVE INSECTS
After death of cacti, land
BECOME PESTS
became economically
valuable for crops again
#3. First classical weed biological success in the US :
St. Johnswort infestation in CA in 1940s, dominating grasslands
Yellow is dense infestation of weed
Two species of Chrysolina beetles (Chrysomelidae) controlled the
weed in the western US in the 1950s and 1960s
Same release site after insects suppressed the weed: a return to
native and economically valuable vegetation
#4. Precedent for CBC of an insect using a pathogen :
Control of the palm pest, rhinoceros beetle, in the South
Pacific with an introduced baculovirus
On Pacific
islands,
coconut
palms are a
basic crop.
Rhinoceros
beetle larvae
feed in and
destroy
palms
An Oryctes virus was found in the pest in Malaysia and introduced to
Western Samoa, using artificially infected females as vectors
Oryctes virus of
rhinoceros beetle on
coconut is one of few
examples of successful
use of an insect
pathogen as a classical
biological control agent
Key biological feature
was survival of infected
females long enough to
vector virus to larval
group feeding sites
#5. Precedent for augmentative BC of greenhouse insects:
Whiteflies are a long standing pest in greenhouse vegetable crops
Whitefly
nymphs
Encarisa formosa showed up
spontaneously and was later
commercially produced
Commercial production methods for E. formosa were developed and
a release card that allowed a repeatable number to be applied
As hung in the greenhouse
As received in the mail
#6. Precedent for biopesticides based on insect pathogens:
Healthy caterpillar vs one killed by Bacillus thuringiensis
healthy
Killed by Bt
#7 Precedent for CBC of Weeds with Plant Pathogen:
Skeleton weed infestations in Australian wheat fields
Close up of skeleton weed plant
Release of skeleton weed rust as a classical biological control agent
MY formative experience with biological control: suppression of alfalfa
weevil by introduced parasitoids in the 1970s
Hypera postica, the
alfalfa weevil, an
invasive insect from
Europe
In the 1970s most alfalfa (millions of acres) in the northeastern US
had to be sprayed once or twice per year to control this insect
Defoliation of alfalfa by alfalfa weevil larvae
Hypera postica, the
alfalfa weevil, an
invasive insect from
Europe
Defoliation of alfalfa by alfalfa weevil larvae
Bathyplectes curculionis, an
ichneumonid from Europe that
attacks H. postica larvae
Microctonus aethiopoides, a braconid that attacks H. postica adults,
reducing oviposition before death
Control was complete
in the eastern US,
eliminating the need for
annual pesticide
applications on millions
of acres alfalfa
Kinds of natural enemies
• Parasitoids (against insect pests)
• Predators (against insects and mites)
• Herbivorous insects and mites (against
plants)
• Pathogens (against insects, mites, plants and
vertebrates)
Parasitoids
Diptera
Hymenoptera
• Tachinidae
• and 11 other minor
families
• Aphelinidae
• Encyrtidae
• and 34 other families
of some importance
TACHINIDAE
Compsilura concinnata an important tachinid parasitoid of browntail moth
APHELINIDAE (Aphytis melinus) on California red scale
PREDATORS
Predatory Insects
Other Predators
• Many orders,
especially species in
• Coleoptera
• Hemiptera
• Hymenoptera
• Diptera
•
•
•
•
•
spiders
mites
snails
small mammals
birds
Coccinellidae- ladybirds-mostly generalist predators
Twicestabbed
ladybird
Phytoseiidaepredaceous
mites
ARTHROPOD PATHOGENS
•
•
•
•
•
Bacteria (e.g., Bacillus thuringiensis)
Viruses (e.g., NPV of gypsy moth)
Fungi (e.g., Beauveria bassiana)
Nematodes (e.g., Steinernema feltiae)
Protozoa (e.g., Nosema sp.)
Bacillus thuringiensis
healthy caterpillar (top) and Bt-killed one (bottom)
Insect cells infected with NPV
Fungus-killed caterpillar
Entomophagous nematode-see stylet
Nematode-killed termite
HERBIVOROUS
ARTHROPODS
•
•
•
•
•
•
MANY FAMILIES
Dactylopidae
Curculionidae
Chyrsomelidae
Tephritidae
Many moth families
Dactylopids are important for control of cacti
Curculionidae-the weevil Crytobagous salviniae
controlled Salvinia molesta