Ground plant fiber, water and other ingredients could prove a recipe for disaster for pesky Formosan subterranean termites. ARS scientists created the recipe—a new bait formula—to trick foraging termites into spreading slow-acting poisons to their nestmates and queen. The Formosan termite is among the most destructive of urban pests, costing residents in Hawaii, California, and 9 southern states about $1 billion annually in repairs and controls. Standard bait systems employ wooden stakes, cardboard or tissue paper to encourage the insects to contact and spread the toxins. But the scientists’ new bait contains powerful new termite feeding stimulants, along with ground-up plant fiber and substances that ensure an environment the termites prefer. The feeding stimulants are made from nutrients and other substances in decaying wood where termites forage for food. Lab studies show that insects find the new bait, or "matrix," more appealing than wood alone. This improves the effectiveness of slow-acting toxins in poisoning the termite colony. In lab studies, the new matrix often stimulated termite feeding within 2 weeks and required up to 95 percent less toxic material to kill the pests than did standard bait systems. ARS has applied for patent protection on the new bait.

Southern Regional Research Center, New Orleans, LA
Guadalupe Rojas, (504) 286-4382, grojas@commserver.srrc.usda.gov

Chinese leaf beetles were released this past summer in experimental field cages in six states as the first step in a biological control program for the invasive weed saltcedar. Saltcedar trees, which can grow up to 30 feet tall, infest more than 1 million acres along rivers and streams throughout the West. The leaf beetles have been tested extensively in China and in U.S. quarantine facilities and eat only Old World species of saltcedar. With the help of many cooperative agencies and university researchers, beetle eggs or larvae were put on caged saltcedar plants at sites in California, Colorado, Nevada, Texas, Utah and Wyoming. Saltcedar was brought into the United States in 1837 to protect streambanks from erosion. But without natural enemies, it has crowded out willows, cottonwoods and other plants crucial to wildlife. Saltcedar trees also degrade wildlife habitat by increasing soil salinity, changing streamflows and increasing wildfire frequency. USDA’s Animal and Plant Health Inspection Service authorized the permits, with concurrence from the U.S. Fish and Wildlife Service, for ARS to release the beetles into cages at selected sites across the western United States. This is the first time biocontrol scientists have targeted a weed that can be important to an endangered animal—the southwestern willow flycatcher. These birds nest in saltcedar in some locations where the trees had replaced their native willow nesting sites. For this reason, ARS will conduct 1 year of field experiments during which the beetles will remain in cages. No beetles will be released near nesting flycatchers without FWS approval. If the beetles are approved for release outside their 10-foot-square cages, they should spread several hundred feet per year to nearby saltcedar plants.

Grassland, Soil and Water Research Laboratory, Temple, TX
C. Jack DeLoach, (254) 770-6531, deloach@brc.tamus.edu
Exotic and Invasive Weeds Research Unit, Albany, CA
Raymond I. Carruthers, (510) 559-6127, ric@pw.usda.gov

A soil-dwelling nematode may help to biologically control house and stable flies that pester cattle and people. Stomoxys calcitrans, the stable fly, is among the top insect pests of dairy and beef cattle. The fly sports a bayonet-like mouth part for drawing blood from cattle. Such attacks can stress cattle, leading to poor weight gain, decreased milk and meat production and crowding behaviors that can overheat the animals. S. calcitrans can also transmit 39 different diseases or parasites. Chemical insecticides are used against both adult flies and maggots, which often develop in manure around cattle feedlots and calf pens. But chemical fly control is costly, and many insecticidal compounds break down after a few days, exposing cattle to further attack by flies from other sources. As an alternative, ARS and university scientists are exploring manure treatments using the nematode species Steinernema feltiae. It’s their top pick from 20 species provided by BioLogic Co., a Pennsylvania firm. In lab experiments, S. feltiae killed up to 99 percent of fly maggots within 48 hours of infection. Feedlot trials begun this spring are helping scientists evaluate BioLogic formulations for protecting the nematode from sunlight and dehydration once applied to manure. They’re also trying to pinpoint where and when to apply the nematode, such as beneath fencing or in early May, start of the fly breeding season.

Midwest Livestock Insects Research Laboratory, Lincoln, NE
David Taylor, (402) 437-5267, dtaylor1@unl.edu

Look-alike water weeds called watermilfoils can now be more easily distinguished at the genetic level, helping weed specialists plan counterattacks. ARS scientists in California and colleagues at the Washington State Department of Ecology conducted the research using samples of the weeds' genetic material, or DNA. In U.S. waterways, the most pervasive milfoil is the exotic Eurasian watermilfoil. It infests lakes and streams and can block delivery of water to cities and farms. It can also make waterways inhospitable to native plants and animals and fishers, boaters and water-skiers. Eurasian watermilfoil, or Myriophyllum spicatum, is found throughout the United States. The researchers took a close look at samples of this and other watermilfoil species from California and Washington. In scrutinizing the weeds' DNA, they found differences between the Eurasian species and four similar-looking but less troublesome relatives. The research team is among the first to use a technique known as RAPD, or Random Amplified Polymorphic DNA, to differentiate among milfoil species. They also used RAPD to detect genetic differences between Eurasian watermilfoil plants from various locales. The differences within this species could prove important if future control programs rely on the weed’s natural insect enemies. The milfoil weevil, Euhrychiopsis lecontei, is a biocontrol candidate for Eurasian watermilfoil. Biocontrol insects often are collected at one site and relocated hundreds, even thousands of miles away. But scientists think these little brownish black insects should be put to work where the target Eurasian watermilfoils are the closest possible genetic match to watermilfoils at the insects’ collection site.

Exotic and Invasive Weeds Research Unit, Davis, CA
Lars W.J. Anderson, (530) 752-6260, lwanderson@ucdavis.edu

ARS researchers and cooperators distributed more than 19 million flea beetles to combat leafy spurge, a noxious weed, during 5 field days as part of Spurgefest ’99. The field days were part of The Ecological Areawide Management (TEAM) of Leafy Spurge. TEAM Leafy Spurge is a 5-year ARS research and demonstration program that focuses on the weed's infestations in the Little Missouri River drainage in Wyoming, Montana and the Dakotas. The costly, noxious weed infests at least 5 million acres in 29 states and Canadian provinces. Infestations double every 5 to 10 years. Cattle won’t eat leafy spurge, and productive rangeland can be rendered useless when it takes over. Ranchers, landowners and land managers took insects from the field days to release on their land as part of an integrated management plan for the weed. During the last decade, ARS scientists imported several species of tiny Aphthona flea beetles from the weed’s Eurasian homeland. In 1988, 80 Aphthona beetles were released at one site in North Dakota. Today, millions of beetles descended from those 80 are helping rein in the weed. The insects don’t eat other rangeland or crop plants.

ARS Northern Plains Agricultural Research Laboratory, Sidney, MT
Gerry Anderson/Chad Prosser, (406) 482-2020
gerry@mail.sidney.ars.usda.gov / chad@mail.sidney.ars.usda.gov

Microorganisms that live in the guts of insects and in the soil may be keys to improving the success of biological control against weeds. Many scientists around the world study and import natural insect enemies to combat invader weeds such as leafy spurge. But consistent success has been elusive. Microbes may be part of the reason. ARS scientists discovered that several insects used as biological control agents for leafy spurge and spotted knapweed harbor bacteria known as Wolbachia. The bacteria affect sperm in the insects, causing offspring to be up to 90 percent female. This skewed gender ratio can reduce the insects' ability to reproduce. Other microbes are valuable insect allies. Flea beetles imported to control leafy spurge have been most successful where native soilborne bacteria and fungi also feed on the weed. That's because microbes invade the roots via wounds made by the insects. Both findings suggest useful tactics for mass laboratory rearing of weed-attacking insects. Scientists are working on lab diets for the insects. In the future, they may try including in these diets a compound to rid insects of undesirable bacteria. Or, they might add beneficial weed-controlling microbes to a diet, so insects would transport them directly to weeds.

Northern Plains Agricultural Research Center, Sidney, MT
Barbara A. Frederick/Anthony J. Caesar, (406) 482-2020
bfrederi@sidney.ars.usda.gov / caesara@sidney.ars.usda.gov

A 5-year study with some 190,000 domesticated honey bees provides new evidence that beekeepers can produce and maintain bee colonies resistant to varroa mites. The mites are eight-legged, blood-sucking parasites—among the worst enemies of the common honey bee, Apis mellifera, worldwide. ARS scientists, working with a commercial beekeeper in Arizona, populated research apiaries with surviving bees from hives not treated with mite-controlling chemicals called miticides. The researchers kept these new hives free of miticides. During the test, the hives averaged only 7 mites per 100 bees. In some years, some hives were free of mites. Other researchers in Mexico, Brazil, Germany and Russia have also found hives of Apis mellifera bees naturally resistant to the mites. The Arizona test provides additional proof that beekeepers and breeders can keep hives free of mites if they use selective breeding to keep their apiaries populated with mite-tolerant stock. Some beekeepers and breeders are already doing this.

Carl Hayden Bee Research Center, Tucson, AZ
Eric H. Erickson, (520) 670-6481, ext. 104, eric@tucson.ars.ag.gov