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Exploring the World for Biocontrol Agents
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In a beautiful valley near Montpellier
in southern France, the European
Biological Control Laboratory is
home to scientists who fight the
battle against Eurasian weeds and
insect pests that have invaded the
United States.
(K9341-2)
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Seasoned travelers, the scientists at
the European Biological Control Laboratory (EBCL) will happily oblige the
curious with a story or two of misadventure. During a recent trip to Nepal, Tim
Widmer learned first-hand just how tricky it can be to shake leeches off your
pants and fingers. Rouhollah Sobhian tells of getting blinded in a Tunisian
sandstorm, while Alan Kirk recalls being stranded in the Australian Outback.
Then, there's Kim Hoelmer, who sampled fried grasshoppers in a Beijing street
market, and Franck Hérard, whose team searched for a "lost"
member in a thick forest only to find him waiting at their hotel.
Listening to these scientists gives the impression that such misadventures are
all part of the job. Aside from world travel, their duties include research on
parasites, predators, and pathogens of insects and weeds that have become
invasive pests of U.S. agriculture. By one estimate, these pests cost about $46
billion annually in losses and control, not counting ecological damage and harm
to wildlife. |
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In southern France, ARS specialist
Rouhollah Sobhian (center) and
technicians Arnaud Blanchet (left)
and Boris Fumanal inspect Russian
thistle for potential biocontrol
insects.
(K9325-1)
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From Montpellier's seaside airport,
EBCL scientists routinely hop flights to the pests' points of origin in North
Africa, the Middle East, the Balkans, and Asia to collect natural enemies.
Typically, they'll explore sites where the crops, climate, or habitat matches a
particular U.S. region where a pest has become established and a biocontrol
agent is needed.
"With all the concern about invasive, nonnative species, we're on the
forefront of the only proven, sustainable technology to deal long-term with the
problems that have already been introduced," says EBCL director Paul C.
(Chuck) Quimby, Jr.
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Well camouflaged, a larva of the
Gymnancylie canella moth burrows
into a Russian thistle stem.
(K9325-3)
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EBCL is about a 20-minute drive from
downtown Montpellier on France's Mediterranean coast. USDA's
Agricultural Research Service (ARS)
established the lab in 1919 and had a new facility built for it in 1999 on a
5-acre plot inside France's prestigious international research campus, called
AGROPOLIS. Administered by ARS's Office of International Research Programs, the
1,800-square-meter lab boasts a top-notch quarantine lab with three
self-contained greenhouses. EBCL's staff at Montpellier and substations in Rome
and Thessaloniki includes 30 scientists, lab technicians, and support personnel
from America, France, Britain, Africa, and elsewhere.
EBCL is like an overseas outpost where the natural enemies of pests that
scientists have collected can be reared, tested, packaged, and shipped
stateside for use in classical biocontrol programs.
Says Quimby, "Our job is first to explore and find natural enemies of
designated targets, and then characterize their identity, biology, and host
range to make sure they're specific enough for introduction into the United
States without causing problems." |
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Entomologist Franck Hérard
inspects gypsy moth larvae
raised on an artificial diet.
Larvae will be placed on oak
trees to trap specific fly
parasites, which will be sent
to U.S. cooperators.
(K9328-1)
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To date, this has resulted in nearly
200 different biocontrol agents for use against at least 36 insect and weed
species plaguing U.S. agriculture and natural habitats. These agents usually
fall into one of four categories:
Parasites—including Peristenus wasp species, whose larvae
develop inside Lygus bug nymph stages.
Predators—such as Thanasimus formicarius, a beetle that eats
pine shoot beetles, a pest established in 12 states and Canada.
Pathogens—such as Trichothecium roseum, a fungus that
infects the exotic shrub saltcedar, which in western states increases soil
salinity and deprives native plants of water.
Weed Feeders—such as the weevils Larinus minutus on
knapweeds and Eustenopus villosus on yellow starthistle. |
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A state-of-the-art quarantine facility
is located next to the European Biological
Control Laboratory. Dominique Coutinot,
quarantine officer and support scientist,
manages the facility under French Ministry
of Agriculture rules.
(K9324-1)
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One EBCL biocontrol success story is
its research on seven parasites and one predator species from western Europe
for control of alfalfa weevils. In the 1980s, these biocontrols were released
in the United States and resulted in $90 million in yearly savings. In Texas's
Rio Grande Valley and southern California, silverleaf whitefly numbers have
declined since 1995, thanks to integrated pest management (IPM) tactics that
include using insect growth regulators and parasite releases. Kirk and Guy
Mercadier contributed further to the $1 billion pest's decline by finding 36
parasite species in explorations to 31 countries, including Spain, the United
Arab Emirates, and Pakistan, from 1991 to 1997.
Currently, EBCL's top weed priorities include yellow starthistle, Russian
knapweed, saltcedar, Russian thistle, leafy spurge, hoary cress, perennial
pepperweed, spotted knapweed, medusahead ryegrass, and rush skeleton weed.
The insect "hit-list" includes diamondback moth, pink hibiscus
mealybug, wheat stem sawfly, gypsy moth, codling moth, apple leafrollers, olive
fruit fly, grasshopper, locust, termites, Asian longhorned beetle, and
Lygus bug. |
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Plant pathologist Tim Widmer sprays
a fungus isolated from yellow
starthistle on a seedling of the
same plant species. The fungus is
harmless to humans.
(K9339-1)
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Codling Moth and Leafroller
Kim Chen, a senior support scientist, is taking aim at codling moths and
several leafroller species. These Eurasian insects are apple and pear pests in
the northwestern United States. Chen's 1999 and 2000 surveys of three orchards
in southern, central, and northern France revealed 65 parasite species,
including braconid wasps and tachinid flies, that attack the pests.
One pest fighter is Colpoclypeus florus, a eulophid wasp that Chen and
technician Jaime Lopez are rearing from collections made in French apple
orchards. They will ship C. florus this spring to entomologist Tom
Unruh, an ARS cooperator in Wapato, Washington, who wants to release a
warm-climate strain of the wasp species. He will also receive a braconid wasp
that parasitizes leafrollers. Unruh notes that previously released parasites of
codling moth in Washington State have already become established. |
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Technician Nicolas Crespy
collects diamondback moth
larvae from the undersides
of wild cabbage leaves.
(K9342-2)
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Lygus Bug, Wheat Stem Sawflies,
and Olive Fruit Flies
In addition to the Lygus bug, which damages alfalfa, cotton, strawberry,
and many other crops, the scientists at EBCL are rearing parasites collected
from wheat stem sawflies and olive fruit flies. Kim Hoelmer, entomologist, and
Dominique Coutinot, senior support staff member, lead this project.
In Montana and North and South Dakota, sawflies cause roughly $100 million
annually in yield losses. Female flies lay their eggs inside the wheat plant's
stem, and emerging larvae eat their way down to the base of the stalk and
excavate it. Weakened plants may topple over so they can't be harvested.
According to entomologist Tom Shanower, an ARS cooperator in Sidney, Montana,
biocontrol is especially appealing against the sawfly because insecticides are
too costly to use in wheat, and resistant wheats, called solid stem varieties,
currently offer poor yields.
Hymenopterous wasps from Eurasia top the list of biocontrol candidates.
Hoelmer's most recent search for them was in Uzbekistan. "This collection
is now overwintering," he reports. "The sawflies and any parasitoids
they harbor will emerge this spring."
Last fall, he and Coutinot went to Tunisia to find olive fruitfly parasites, of
interest to Charles Pickett, a California Department of Food and Agriculture
(CDFA) cooperator. As the fly's population soars, Pickett sees an emerging
threat to California's $33.9 million olive industry that will require
biocontrol and other IPM tactics to minimize pesticide costs and environmental
harm.
Before the fly's arrival, "California olive growers never had to worry
about something getting into the fruit," says Pickett, who hopes to import
new parasites in addition to one he's already test-released—Psyttalia
concolor. Hoelmer says, "We found the flies at two different sites and
made nice collections, from which we've already gotten two different
parasitoids."
Asian Longhorned Beetles
Franck Hérard, an entomologist, will be exploring Europe to identify
natural enemies of cerambycid beetles. He hopes these enemies will be useful
biocontrols for battling Asian longhorned beetles. Hérard is working in
cooperation with Michael Smith, an entomologist with the ARS Beneficial Insects
Introduction Research Laboratory (BIIRL), in Newark, Delaware.
The Asian longhorned beetle made its U.S. debut in New York's Central Park in
1996 and turned up 2 years later in Chicago's Lincoln Park. Between the two
cities, 6,400 trees have since been removed, notes Smith. Unchecked, the pest
poses a $3.8 billion threat to North America's hardwood and ornamental trees,
according to USDA's Animal and Plant Health Inspection Service (APHIS).
While Hérard scours Europe for promising new associations involving
cerambycids and parasitoids, Smith's search for natural enemies will focus on
the beetle's closest U.S. relatives. Chinese cooperators, meanwhile, will
search for enemies that co-evolved with the pest in its native Asia.
Leafy Spurge, Russian Thistle, and Spotted Knapweed
The efforts of Rouhollah Sobhian, now retired from EBCL's biocontrol research
team, included biocontrol agents for leafy spurge and Russian thistle (also
known as tumbleweed). One agent, a gall midge called Spurgia capitigena,
will be released by ARS cooperators in Montana against leafy spurge. Another
promising biocontrol is Gymnancylie canella, a moth that in the
caterpillar stage eats tumbleweed shoots and seeds.
Although an icon of the American West, tumbleweed is an invasive species some
landowners consider a rangeland pest because of its prodigious seed production,
flammability, wind-driven tumbling, and thorny stems. Says Sobhian, whose
tumbleweed work is funded by CDFA, "It blows against fences, blocks
waterways, and is said to cause accidents on highways."
Sobhian says more studies are needed on G. canella's overwintering
habitat and host specificity before its value as a biocontrol can be fully
ascertained.
Sobhian's successor, René Sforza, is renewing a spotted knapweed project
in which he'll conduct explorations for biocontrols in Ukraine and
Russia—areas formerly restricted during the Cold War. Sforza is also
starting a new medusahead ryegrass project.
Saltcedar, Yellow Starthistle, and Other Invasive Weeds
Besides studying giant reed, plant pathologist Tim Widmer and technician Fatiha
Guermache are looking for pathogens that cause root and foliar diseases on
saltcedar, yellow starthistle, and other invasive weeds. "A plant
pathogen," Widmer explains, "is most commonly a fungus, bacterium,
virus, nematode, or an abiotic factor, such as ozone or pollution, that
continuously disrupts the plant's normal processes."
At CDFA, Widmer's cooperators are interested in pathogens as an alternative to
controlling yellow starthistle with herbicides. First detected in the
mid-1800s, the thistle now infests 10 million acres in California. Since
spreading to other western states, it has become a pest of rangelands,
prairies, vineyards, roadsides, and natural habitats. Uncontested, it displaces
native grasses and plants that sustain livestock and wildlife. Widmer is
currently testing more than 20 fungal strains and 45 bacteria isolated from
thistle specimens and soils he collected in France earlier this year.
Pink Hybiscus Mealybug
Entomologist John Goolsby (of the ARS Australian Biological Control Laboratory)
and Kirk are exploring Australia, Egypt, Hong Kong, Macau, and other places to
collect natural enemies of pink hibiscus mealybug, a soft-bodied pest that
attacks 200 different plants.
Because of its broad appetite and insecticide-blocking waxy coat, the bug's
1999 U.S. arrival in California caused much alarm. APHIS cooperators led by
Dale Meyerdirk countered with timely parasite releases, including Anagyrus
kamali wasps from the scientists' Australian collections. This action
helped curb mealybug numbers by 98 percent, staving off millions of dollars in
losses.
Genes Identify Good Inside the Bad
Molecular biologist Marie-Claude Bon and senior support scientist Nathalie
Ramualde are working on genetic characterizations of biocontrol agents and
their hosts. One objective is to customize biocontrol strategies based on
genetic information about target pests and their natural enemies. They've also
begun developing molecular diagnostic tools to detect and monitor parasitism
and differentiate among parasites, including Peristenus wasps—some
species of which have already been introduced into the United States and Canada
for Lygus bug control.
"We're developing a tool to detect the presence of parasitoid DNA
extracted from the host nymphs," says Bon. They use genetic fingerprinting
technologies similar to those used in crime labs, such as the polymerase chain
reaction.
Formulating Hardy Fungi
Insect pathologist Guy Mercadier and Quimby, along with technician Nicolas
Crespy, are testing new ways to formulate fungi into biopesticide products.
They have a handy source of microbes to choose from. Since about 1988,
Mercadier has amassed 1,000-plus strains of Beauveria, Metarhizium,
Paecilomyces, and other fungi isolated from silverleaf whiteflies,
diamondback moths, codling moths, African locusts, coffee berry borers, and
other insect pests.
The researchers also developed a procedure to make M. anisopliae more
resistant to drying. In arid regions like Africa's Sub-Sahara, for example, the
sun can prevent this fungus from germinating inside its insect hosts. Called
the "stabileze" method, their approach calls for shocking the
fungus's spores with a dose of sucrose and ethanol, which removes up to 80
percent of cellular water.
"If we devise a good method of formulating a fungal pathogen that's
resistant to UV light, high temperature, and degradation in storage," says
Quimby, "this technology can probably be used with other fungi against
other target insects in the United States."
Passing the Test
Once a parasite, predator, or pathogen has been deemed a worthwhile biocontrol
candidate, EBCL scientists carefully package it for quarantined shipment to one
of three ARS locations stateside.
The first stop for insects and insect pathogens is either the BIIRL or ARS'
Stoneville (Mississippi) Research Quarantine Facility. Weed pathogens go to
ARS' Foreign Diseases-Exotic Weed Science Unit, in Fort Detrick, Maryland.
New arrivals must pass a stringent inspection before they're sent to EBCL's
cooperators, which include other ARS labs, state agriculture departments, other
USDA agencies (including the Forest Service) and non-USDA agencies in the
Department of the Interior. The list includes state and land-grant
universities, with cooperators in Oregon, California, North Dakota, Montana,
Wyoming, Colorado, Illinois, and Kentucky.—By
Jan Suszkiw,
Agricultural Research Service Information Staff.
This research is part of Crop Protection and Quarantine, an ARS National
Program (#304) described on the World Wide Web at
http://www.nps.ars.usda.gov.
To reach scientists mentioned in this story, contact
Jan Suszkiw, USDA-ARS Information
Staff, 5601 Sunnyside Avenue, Beltsville, Maryland 20705-5129, phone (301)
504-1630, fax (301) 504-1641. |
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"Scientists in Montpellier are Exploring the
World for Biocontrol Agents" was published in the
April 2001
issue of Agricultural Research magazine.
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