Microbial “weed wackers” imported from abroad could be in store for yellow starthistle, mile-a-minute, and other invasive plants that have encroached on crops, rangeland, parks, pastures, and privately owned lands. The microbes, which include fungi, bacteria, and viruses, for example, sicken the destructive weeds by causing disease. Because they are of foreign origin, like their weedy hosts, the microbes undergo a battery of tests to ensure they’ll pose no danger to crops, domestic plant relatives, or the environment. The biocontrol “boot camp” in which such studies take place is the ARS Foreign Disease-Weed Science Research Unit in Fort Detrick, MD. The nation’s largest facility for studying whole plants under microbial containment conditions, the ARS lab is the first stop in a national, multiagency campaign to reunite invasive weeds with natural enemies from their homelands. One microbial recruit to pass muster is the rust fungus Puccinia carduorum Jacky. Released in 1987 in Virginia, it has since worked with the seed head weevil, Rhynocyllus conicus, to hold down exotic musk thistle populations—its natural host—that were reduced by up to 90 percent in some regions by the release of the weevil in the late 1960s. Biocontrol agents like Puccinia are seen as long-term alternatives to chemical and other controls because of cost, environmental concerns, and other reasons.

Foreign Disease-Exotic Weeds Research Unit, Fort Detrick, MD
William Bruckart, (301) 619-7340, bruckart@asrr.arsusda.gov

A soil-dwelling fungus may be the answer to naturally controlling tiny fly maggots that pester sugar beet crops. Nearly half the nation’s 1.5-million-acre sugar beet crop is treated with granular insecticides to kill the maggot offspring of the fly, Tetanopsis myopaeformis. Unchecked, the quarter- to half-inch-long maggots damage the beet’s roots, which supply about 35 percent of the nation’s sucrose. The problem is, some insecticides now used can be toxic to sugar beet seedlings. Also, use of the chemicals can harm nontarget insects in treated soil areas. As a safer alternative, ARS and U.S. Environmental Protection Agency scientists are testing use of Syngliocladium tetanopsis. It’s a species of fungus that infects and kills the maggots. In lab tests, more than 95 percent of newly hatched maggots died within 5 days of exposure to the fungus. Larger, final-stage maggots lived for several weeks, but few survived. Small-scale field studies indicate the fungus’ cigar-shaped spores could be sprayed or soaked into soil or coated directly onto beet seeds. In host-specificity studies, ladybugs, lacewings, Colorado potato beetles, and other nontarget insects survived exposure to the fungus, indicating that it’s highly selective. Researchers are now seeking a commercial company to help further explore the fungus’ potential as a biological pesticide product.

Molecular Plant Pathology Laboratory, Beltsville, MD
Ann Smigocki, (301) 504-5848, smigocki@asrr.arsusda.gov

A tiny moth from Australia is the first insect sent to the United States for possible use in fighting Old World climbing fern, an invasive weed that threatens Florida’s Everglades and other native ecosystems. The fern, Lygodium microphyllum, blankets trees when it climbs up their trunks, creating massive, high walls of light-green vegetation. It smothers lower growing plants by forming a tough, spongy mat. The moth, currently known as Cataclysta camptozonale, measures only one-half inch from wingtip to wingtip. Its slender, wormlike larvae munch on fern leaves. Scientists at ARS' Australian Biological Control Laboratory subjected the insect to rigorous tests with climbing fern and 14 other fern species, then sent more than 250 moths for other tests by ARS researchers in Florida and their University of Florida colleagues. If follow-up tests at the U.S. and Australian labs confirm that the moth won’t harm native or crop plants, scientist may seek federal and state permission to set the insect free at fern-infested sites in Florida.

ARS Australian Biological Control Laboratory, Indooroopilly, Queensland, Australia
John A. Goolsby, 617 3214 2821, john.goolsby@brs.ento.csiro.au

ARS Invasive Plant Research Laboratory, Gainesville, FL
Gary R. Buckingham, (352) 372-3505, ext. 124, grbuck@nervm.nerdc.ufl.edu

A new flea beetle species found in Russia has potential to control the noxious, invasive leafy spurge weed. 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. At least six species of flea beetles belonging to the genus Aphthona have been introduced and released in North America as control agents for leafy spurge. Now, ARS scientists working with Russian and Italian researches have discovered, described, and illustrated a new species, A. russica, and distinguished it from related species—especially those which feed on leafy spurge. Their report includes new information on several other species of Aphthona that could be used in biological control of weeds. Correctly identifying the new beetle will aid foreign exploration for other new beneficial insects, quality control of laboratory cultures, and follow-up assessment of the spread and impact of beneficial insect species released for biological control of weeds.

Systematic Entomology Laboratory, Washington, DC
Alexander S. Konstantinov, (202) 382-1790, akonstan@sel.barc.USDA.gov

Two new insects may join the dozen existing biological control agents against leafy spurge, Euphorbia esula, thanks to ARS research in Europe. ARS scientists in France have discovered that a midge, Spurgia capitigena, lays eggs near the tip of leafy spurge stems. Developing larvae cause the plant to form a swelling, or gall, and turn up its leaves. The gall, which provides food for the midge larvae, reduces the weed’s ability to produce seeds. The researchers have obtained necessary permits and hope to release the midge early this summer. A stem-boring beetle, Thamnurgus euphorbiae, is next in line on the spurge control team. ARS researchers at the European Biological Control Laboratory and cooperators showed that the Italian beetle tunnels into spurge stems to lay eggs. The larvae that hatch chew into the stems, weakening the plant and reducing seed production. The beetle has gained support from the Technical Advisory Group for Biological Control Agents of Weeds, an independent committee that counsels the USDA’s Animal and Plant Health Inspection Service on whether to approve release of a pest control agent. If APHIS grants a permit, the beetle could be released in 2001. Both insects have been tested for efficacy against spurge and to ensure they will not harm other vegetation. Unlike existing agents, the new midge and beetle are expected to thrive in sandy, shady, or moist soils. That should give land managers new options for spurge management along streams and rivers.

Northern Plains Agricultural Research Center, Sidney, MT
Neal R. Spencer, (406) 482-2020, nspencer@sidney.ars.usda.gov

European Biological Control Laboratory, Montpellier, France
Paul C. Quimby, (334) 9962-3000, quimby@cirad.fr

Listening to the loud munching sounds of Asian longhorned beetles may give scientists a clue as to which trees are infested. This is just one of several new tactics that ARS scientists are exploiting to find ways to control or destroy these wood-boring pests. First found in the United States infesting trees in New York in 1996 and in Chicago in 1998, Asian longhorned beetles (ALB) have been intercepted at ports in 17 states. If Anoplophora glabripennis spreads unchecked into U.S. urban and forest landscapes, it could cost billions of dollars in damage. So far, the only solution to the problem has been to cut down and remove infested trees. An ARS entomologist in Newark, DE, is fast becoming one of the world’s experts on these pests. To date, he has uncovered new information never before recorded on ALB behavior. He and colleagues at the State University of New York-Syracuse are working with a specialist on a feeding noise recognition system. It would generate an acoustic “fingerprint” as the beetle larvae feed within the two different tree tissues that they commonly inhabit—inner bark and inner wood. Scientists are also developing an archive of the insect-munching sounds created by other chewers, such as carpenter ants, within ALB-infested trees. They hope to have a functional prototype detection system by early this fall.

Beneficial Insects Research Laboratory, Newark, DE
Michael T. Smith, (302) 731-7331, ext. 41, mtsmith@udel.edu

A trip to Mexico in the summer of 1999 has resulted in the discovery of several natural biocontrol parasites of a new, invasive insect pest. In July 1998, a scientist confirmed that an insect collected from a hibiscus plant in Bradenton, FL, was Paracoccus marginatus—the papaya mealybug. The Bradenton sample was the first time the papaya mealybug had been found in the continental United States. It’s considered to be a serious pest of papaya on several Caribbean Islands and has also been reported to damage papaya and cassava in Mexico. In June 1999, APHIS sent the expert to Mexico to search for possible controls. The experts collected 40 samples of parasites that included three wasps with potential as biocontrol agents. Live samples of the wasps and other potential biological control agents were also sent to ARS scientists in the Beneficial Insects Research Unit at Newark, DE, where the parasites could be reared in quarantine. After screening them and studying their life cycles in living cultures, the Newark scientists have obtained APHIS approval to ship wasp populations to St. Thomas, the U.S. Virgin Islands, where APHIS released them this spring in papaya fields for monitoring and behavioral studies.

Systematic Entomology Laboratory, Beltsville, MD
Douglass R. Miller, (301) 504-5895, dmiller@sel.barc.usda.gov

Natural enemies of the Russian wheat aphid are now established in six states. Ten years after ARS scientists and collaborators released millions of exotic wasp parasites in small grain fields in eastern Colorado to control the Russian wheat aphid, they’ve found that four wasp species have become established in six states. Since invading the United States in 1986, the green, 1/16-inch-long Russian wheat aphids have caused more than $1 billion in insecticide costs and related losses. Conventional breeding has produced aphid-resistant wheat varieties, which are now available to producers. In 1988, to screen natural controls for the Russian wheat aphid, ARS scientists worked with a consortium of federal and state scientists to release 11 species of wasps. Key to the success of the project was the collection of these exotic enemies by the staff of the ARS European Biological Control Laboratory, Montpellier, France. The wasps were released in the wheat- and barley-growing areas of the western United States. The 11.8 million parasitic wasps released represented more than 80 geographic strains collected from 25 different Eurasian countries where the aphid originated. From 1991 through 1993, ARS scientists working with USDA’s Animal and Plant Health Inspection Service, the Colorado State Agricultural Experiment Station, and the Colorado Department of Agriculture conducted an intensive biological control release program. Its purpose: to establish natural enemies of the aphid in small grains in eastern Colorado. That group released seven wasp species into Russian wheat aphid-infested wheat fields. Now, 7 years later, ARS scientist report that four of the seven wasp species have become established throughout a six-state area—Colorado, Kansas, Montana, Nebraska, Oklahoma, and Wyoming. Three species were found parasitizing greenbugs—an aphid relative—on sorghum. Two species successfully parasitized the Russian wheat aphid on wild grasses that aphids used as host plants over summer. Establishing natural enemies as part of integrated pest management systems is important because they do not cost anything, are highly compatible with plant resistance, and can contribute considerably to the overall reduction in the reliance on insecticides to control aphid cereal pests.

Plant Science and Water Conservation Research Laboratory, Stillwater, OK
John D. Burd, (405) 624-4141, ext. 223, jburd@ag.gov

ARS and Louisiana Tech University scientists have found that a fungus which grows on the sicklepod plant effectively controls kudzu. Kudzu is a weed native to eastern Asia that has crept over more than 7 million acres in the United States. In greenhouse and field studies, the scientists found that the fungus Myrothecium verrucaria killed 100 percent of kudzu. In ARS tests, the fungus effectively controlled the weed at different growth stages and under varying physical and environmental conditions. The weed was originally promoted for erosion control and as an inexpensive forage for livestock. It is now present from Florida to New York and westward to central Oklahoma and Texas, with heavy infestations in Alabama, Georgia, and Mississippi. The weed resembles a giant beanstalk. It spreads about 120,000 acres a year, and control costs increase by nearly $6 million annually. Typical—but not highly efficient—control methods include treating with herbicides and mowing. Many consumers are reluctant to spray herbicides, and mowing doesn’t kill the weed’s underground root system. ARS’ bioherbicide appears to invade the plant’s roots. The researchers are doing extensive toxicological studies on the fungus and plan to pursue a patent.

Southern Weed Science Research Unit, Stoneville, MS
C. Douglas Boyette, (662) 686-5217, dboyette@ag.gov