Foreign Agents Imported
for Weed Control
Although pretty at certain times
of the year, saltcedar is an
invasive exotic weed that is
harming both agriculture and
the environment. Here, it is
overtaking native vegetation
along the Gila River in Arizona.
You enter through a thick, metal
door. When it closes, only a small window provides light in the room. Next, you
go through another door into a room with another small window. The goal: to
lure potential escape artists toward a trap in the window rather than allow
them to sneak outside.
Through a third door, you enter a network of laboratories and greenhouses
that hold beneficial insects from foreign lands. These insects, scientists and
landowners hope, may help control some of the United States' worst weed
invaderslike leafy spurge, saltcedar, and melaleuca.
"Invasive species, including weeds, cost U.S. consumers and producers
billions of dollars each year," says Ernest S. Delfosse, the
Agricultural Research Service's national
program leader for weed sciences in Beltsville, Maryland. "Natural enemies
from the weeds' homelands may be our most effective and economical tools for
When beneficial insects arrive from overseas, they are carefully sorted,
screened for parasites, and reared in quarantine facilities like the one just
described, which is located at ARS' Western Regional Research Center in Albany,
Technician Eve Lednicky
examines beneficial insects
being evaluated within the
containment portion of the ARS
quarantine facility in Albany,
Though the specifications may
differ, about two dozen U.S. quarantine facilities serve as strictly regulated
gateways for importing biological control agents. Researchers at some locations
focus on beneficial insects like wasps to control insect pests such as alfalfa
weevils or gypsy moths. Those at other locations look at diseases and other
microscopic agents for both weed and insect control.
This story highlights ARS research on using beneficial insects for
biological control of weeds. ARS operates laboratories with quarantine
facilities in Albany; Stoneville, Mississippi; and Temple, Texas. New
quarantine operations will open in Fort Lauderdale, Florida, and Sidney,
Montana, within the next few years.
ARS also collaborates with universities and other state and federal agencies
that run additional quarantines, including a long-term program at Gainesville,
Florida. Each uses a variety of traps, doors, entryways, and sanitizing
procedures to keep the insects inside until they are intentionally released on
approved weed targets.
In quarantine tests, potential biological
control agents are confined in small
cages with a test plant (Scotch thistle,
in this case) to confirm whether they
will feed and reproduce on that plant.
Biological control aims to restore
some of a weed's natural complement of enemies, making it less damaging here.
This approach has been used successfully and safely for many years. Since 1945,
more than 110 insect species have been released in the continental United
States and Hawaii against some 57 weeds. Some of the worst pests no longer
cause significant damage. "Of course, we have to ensure that we protect
our natural resources at the same time," Delfosse says. "The
quarantine facilities are just one of the steps we take to keep biological
In tandem with the domestic laboratories, ARS operates or collaborates in
the operation of several overseas laboratories for hands-on discovery and
collection of the weeds' natural enemies (see story on ARS' foreign biological
control laboratories, page 7). These labs are in Montpellier, France;
Hurlingham, Argentina; Beijing, China; and Indooroopilly, Australia. Often
working with local landowners and biologists, ARS researchers look for the
insects that will likely do the most damage to the weed and the least damage to
anything else. Scientists at the foreign labs study the basic biology of the
insect agents. They verify that the insects significantly damage the weed and
begin testing to make sure the insects don't eat or reproduce on U.S. native or
Aphthona flava flea beetle feeding on leafy spurge.
Together with hundreds of
cooperators here and overseas, ARS quarantine and foreign research laboratories
serve as an invaluable pipeline for identifying, testing, importing, and
releasing biological control agents against some of our most troublesome weeds.
USDA's Animal and Plant Health Inspection Service (APHIS) plays a key role in
regulating the importation of all beneficial organisms, as well as overseeing
quarantine facilities. Several examples highlight this unique research conduit.
A Key Strategy for TEAM Leafy Spurge
First identified in the United States in 1827, leafy spurge (Euphorbia
esula) now infests at least 5 million acres in 35 states and Canadian
provinces. The weed degrades grazing lands for livestock and wildlife and
reduces land values.
ARS began research on biological control of leafy spurge in the 1970s at
laboratories in California, Montana, and Italy. Since then, ARS, APHIS, and
foreign cooperators have discovered, imported, and released 12 natural enemies.
Leafy spurge overtaking a natural hillside in Colorado.
The stars so far have been a group
of four related flea beetles from Eurasia that belong to the genus
Aphthona. The beetles have rapidly expanded from some areas. At one site
in North Dakota, where 77 beetles were released, about 2 million were harvested
in 1999 for distribution to other spurge-infested areas.
The young beetles burrow into the weed's roots. Adults feed on the leaves.
In addition to harming the plant directly, this feeding allows invasion by
disease-causing fungi or bacteria and impairs its reproduction. "There is
no question that biological control will be a key to long-term control of leafy
spurge," says Neal R. Spencer, an entomologist who leads research at ARS'
Northern Plains Agricultural Research Station in Sidney, Montana.
Mealybugs (Trabutina mannipara)
are being considered as a
biological control agent for saltceder.
These egg sacs are on saltcedar
in quarantine at Temple, Texas.
To demonstrate biological control
and other integrated pest management (IPM) techniques for leafy spurge, ARS
formed The Ecological, Areawide Management (TEAM) Leafy Spurge project in 1997.
ARS and APHIS coordinate the project, with participation by dozens of other
federal, state, and local organizations and ranchers.
TEAM Leafy Spurge is the third in a series of ARS-funded, 5-year IPM
projects but the first to target a weed. Researchers examine biological,
cultural, and chemical methods individually and in combination to manage the
weed. The goal is to find the best tools, from an environmental and economical
standpoint, so ranchers and land managers can reclaim rangeland lost to the
weed and slow its further spread.
"So far, the project has been a big success," says Spencer. Last
summer, TEAM Leafy Spurge distributed for release more than 22 million flea
beetles to 206 ranchers and land managers from 50 counties in 7 states.
The Aphthona beetles will soon be joined by a gall midge, Spurgia
capitigena. Unlike flea beetles, the midge prefers moist, shady areas. That
will give TEAM Leafy Spurge another tool to slow spurge growth in areas where
beetles, grazing sheep and goats, or pesticides aren't effective or practical.
Rouhollah Sobhian, an ARS entomologist, has located a good natural source of
the midge in southern France. Scientists in Europe and Montana have studied the
midge, and Spencer has already obtained a release permit from APHIS.
In Kazakhstan and western China,
the midge Psectrosema noxium
attacks saltcedar and forms galls
on it, killing the terminal stems.
Chinese Beetles for Saltcedar Control
Landowners in the western United States brought in bushy, deciduous
saltcedar (Tamarix spp.) trees for erosion control in 1837. Since then,
saltcedar has crowded out native trees like willows and cottonwoods along parts
of nearly every western river.
In 1987, ARS launched a project to use biological control against the weed.
ARS researchers, along with cooperators in China, France, Israel, Kazakhstan,
and Turkmenistan, began plant studies and identified potential natural enemies.
A leaf beetle, Diorhabda elongata, and a mealybug, Trabutina
mannipara, were shipped to ARS quarantine labs in Albany and Temple for
The leaf beetle Diorhabda elongata
is the first approved biological
control agent for saltcedar
in the United States.
Last summer, the beetle was
approved as the first biological control agent for saltcedar. The adults and
young feed on saltcedar leaves, repeatedly defoliating the tree and depriving
it of nutrients.
Normally, control agents are approved for direct release into target areas.
But this time, researchers faced a unique complication.
"Saltcedar replaced native willows that an endangered birdthe
southwestern willow flycatcher (Empidonax traillii extimus)relied
on for nesting," says ARS entomologist Jack DeLoach. "The bird has
since adapted to nesting in saltcedar, so we have to ensure that the beetles
won't remove the weed faster than we can reestablish native plants for the
birds." DeLoach is in the ARS Grassland Protection Research Unit at
Oxyops vitiosa, a leaf weevil,
is thriving on invasive melaleuca
in southern Florida.
To protect the bird while
controlling the weed, the scientists implemented an extra step, in concurrence
with APHIS and the U.S. Fish and Wildlife Service: a 3-year experimental phase
that begins with the beetles in cages. This will allow scientists to monitor
the rate at which the beetles damage the saltcedar before the insects are
relocated to other critical habitats.
A consortium of experts from more than two dozen federal, state, and local
agencies; universities; and conservation organizations meets periodically to
develop monitoring protocols, review progress, and address concerns.
Despite the endangered species concerns, scientists are confident that the
biological control approach is the right choice for managing saltcedar.
"Saltcedar is an Old World plant with no close native relatives
here," says ARS entomologist Raymond I. Carruthers. "More than 200
natural enemies of saltcedar have been found in China and the former Soviet
Union. Insects like the Diorhabda beetle feed exclusively on saltcedar,
making them ideal for biological control." Carruthers leads the Exotic and
Invasive Weed Research Unit at Albany.
Near Fort Lauderdale, Florida,
50-foot-high melaleuca trees
threaten to destroy the delicate
ecosystem of the Everglades.
The next likely candidate will be
a weevil from France, China, and Kazakhstan, belonging to the genus
Coniatus. Like the Diorhabda beetle, the larvae eat the foliage.
But young Coniatus pupate on the tree before they emerge as adults,
while Diorhabda fall to the ground to pupate and can be drowned in wet
Both the leafy spurge and saltcedar projects are using high-tech tools such
as aerial photography, remote sensing, and geographic information systems
(GIS), to map the weeds over vast areas. ARS ecologist Gerry Anderson in Sidney
and ARS rangeland scientist Jim Everitt at Weslaco, Texas, coordinated some of
"It is often difficult to determine the extent and distribution of weed
populations on rangelands because of the expanse and inaccessibility of these
areas," Anderson says. "These technologies will provide a
comprehensive way to measure the rate at which the weeds spread and the
long-term effectiveness of biological control over wide regions."
Showing Promise for Water Weeds and Melaleuca, Too
Foreign aquatic plants have also invaded and become weeds. ARS began its
search for biological control agents of water weeds by establishing
laboratories in Florida in 1959 and Argentina in 1962. Water-hyacinth was one
of the original targets and remains a high priority today.
By 1992, water-hyacinth had invaded hundreds of lakes and streams throughout
the South and parts of the West and Hawaii. The weed impedes water's natural
flow and can destroy native communities of aquatic plants and animals.
Biological control has already greatly reduced water-hyacinth in Florida,
Louisiana, and Texas, but more agents are needed.
ARS researchers here and abroad are discovering and testing what they hope
will be a new South American team of natural enemies (see story on page 10 in
The Scotch thistle weevil from
Spain is being evaluated in the
Albany quarantine facility to
determine if it is safe for
release in the United States.
Also under way is a promising
project to curb melaleuca, Melaleuca quinquenervia. A tiny, grey-brown
weevil called Oxyops vitiosa is now thriving in at least 50 sites in
south Florida, thanks to more than a decade of work by ARS scientists there and
in Australia. Researchers hope the leaf-eating Oxyops will stop the
spread of melaleuca, a fast-growing tree that crowds out native vegetation and
is threatening to take over Florida's Everglades.
Both melaleuca and O. vitiosa, the melaleuca leaf weevil, are native
to Australia, but neither is a pest there. ARS scientists turned the
1/4-inch-long weevil loose at 13 melaleuca-infested sites in Florida in 1997,
after exhaustive greenhouse testing and investigations by colleagues in
Australia showed the insect would not attack other plants. (See
"Aussie Weevil Opens Attack on
Rampant Melaleuca," Agricultural Research, December 1997, pp.
"Although it's too early to call the weevils a success," says ARS
entomologist Ted D. Center, "all indications are that they are doing
great." Center leads the ARS Aquatic Weed Control Research Unit at Fort
"One site where we originally released 3,300 weevils," he says,
"now has about 80,000. We collected about 20,000 weevils there and
relocated them to 30 new sites. That means we've now placed weevils throughout
melaleuca's entire Florida range.
"In general," Center says, "the weevils have done well at
sites that are dry or only seasonally wet. But at permanently inundated areas,
they may drown when trying to find soil in which to pupate."
But other biological control agents that might thrive at those soggy sites
could be waiting in the wings. After all, the melaleuca-munching weevil was
only one of more than 450 plant-eating critters that scientists at the ARS
Australian Biological Control Laboratory in Indooroopilly, near Brisbane, found
feeding on melaleuca. Today, the team is focusing its melaleuca research on six
of the most promising agentssome of which have already been shipped to
Gainesville, Florida, for in-quarantine scrutiny by a team of ARS scientists
led by entomologist Gary Buckingham.
"Our ongoing field research in Australia ensures that ARS scientists in
Florida have the widest possible array of biological control agents to work
with," says entomologist John A. Goolsby, director of the ARS Australian
Biological Control Laboratory. "This dual-continent approach," he
says, "invites success."By
Kathryn Barry Stelljes and
Marcia Wood, 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
Scientists mentioned in this story can be contacted through
Kathryn Barry Stelljes, USDA-ARS
Information Staff, 800 Buchanon St., Albany, CA 94710; phone (510) 559-6069,
fax (510) 559-5882.
ARS' Foreign Biological Control Laboratories
Gateways to Domestic Weed Control
USDA has a long history of foreign exploration for natural enemies of U.S.
Biological control agents from virtually anywhere in Europe, Asia, or Africa
may make their first stop at ARS' European Biological Control Laboratory in
Montpellier, France. EBCL is USDA's largest and only wholly owned laboratory on
foreign soil for identifying and testing potential beneficial insects for
importation into the United States.
USDA established its first foreign laboratory in 1919 outside of Paris,
France. In 1958, the Rome, Italy, location began working on weeds, followed by
another established in Greece in 1980.
In 1991, the laboratories in Rome and Paris consolidated to form the ARS
European Biological Control Laboratory in Montpellier, France, but are still
maintaining small substations in Rome and Thessaloniki, Greece.
In 1999, new construction was completed at the Montpellier site, including a
1,600-square-foot quarantine facility for screening insects and a
400-square-foot facility for plant pathogens. Originally, since the laboratory
studied insects and weeds present in France, quarantine was not needed. But now
the lab handles insects from several continents, so quarantines were set up to
protect the French environment.
The lab has introduced and is currently studying nearly 200 biological
control agents that help control at least three dozen crop-damaging insects and
Major weed targets now include leafy spurge, saltcedar, Russian and yellow
starthistle, Russian knapweed, and perennial mustards such as hoary cress.
"This unique resource has paid for itself many times over by enabling
researchers to find and test natural enemies of weeds," says Paul C.
Quimby, the ARS weed scientist who runs EBCL. "With our new quarantine
facility, the lab will provide an even greater service."
ARS also supports biological control laboratories in Asia, Australia, and
USDA's Asian Parasite Laboratory, originally located in Japan and then moved
to South Korea, performed biological control studies from 1922 to 1993 (with a
gap between 1941 and 1975). Researchers at this laboratory helped discover and
test agents for control of leafy spurge and saltcedartoday's emerging
To continue research in Asia, ARS and the Chinese Academy of Agricultural
Sciences established the Sino-American Collaborative Biological Control
Laboratory in Beijing, China, in 1988. Today the lab works on agents to control
saltcedar, leafy spurge, several aquatic weeds, and some insect pests.
In 1989, ARS opened the Australian Biological Control Laboratory near
Brisbane, in cooperation with the Commonweath Scientific and Industrial
Research Organization (CSIRO). The mission of this lab is to evaluate
biological control agents for weeds of Australian and Southeast Asian origin.
Researchers there have discovered biological controls for many of the invasive
wetland and aquatic weeds in the southern and western United States, such as
melaleuca, Old World climbing fern, and hydrilla. Onsite CSIRO quarantine
facilities allow ARS researchers to rear insects for preliminary testing.
The ARS South American Biological Control Laboratory near Buenos Aires,
Argentina, opened in 1962 to tackle alligatorweed and water-hyacinth. Research
there has since expanded to include waterlettuce, tropical soda apple, and
other tropical weeds, rangeland weeds, and insect pests such as fire ants.
"Foreign Agents Imported for Weed Control"
was published in the March 2000 issue
of Agricultural Research magazine.