An insect chemical that prompts corn seedlings to send out a distress signal has been chemically isolated, identified and artificially reproduced by ARS and cooperating scientists. The chemical, called volicitin, is secreted in the saliva of beet armyworm caterpillars and other similar pests that feed on crops. The researchers say volicitin causes plants to produce chemical aromas, which in turn lure beneficial insects to attack the crop pests. The finding is the latest in an ongoing research effort to find environmentally friendly ways to control crop pests. In lab studies, scientists extracted volicitin from the saliva of beet armyworms. The researchers then cut corn seedling leaves and dabbed volicitin onto the damaged leaf areas. The researchers found that volicitin induced the seedlings to give off chemical aromas that act like distress signals. The plant chemicals lured a beneficial wasp, Cotesia marginiventris, that attacked the caterpillar pests. Simply damaging the seedling leaves--without adding volicitin--did not induce the same "SOS" response. ARS has filed a patent application on the volicitin compound. Scientists said the discovery could help plant breeders develop new crop varieties with enhanced chemical defense systems. Plants would be better able to attract beneficial insects that could fend off the attacking pests, cutting down on pest damage and allowing farmers to reduce pesticide applications to control crop pests. (PATENT APPLICATION 08/757,701)
Center for Medical, Agricultural and Veterinary Entomology, Gainesville, FL
James H. Tumlinson,(352) 374-5730, tumlinson@gainesville.usda.ufl.edu

An organism that infects fire ants with a slow-acting disease has been discovered for the first time in the United States. The organism, called Thelohania solenopsae, is a microsporidium that the queen spreads to her offspring through her eggs. Ants thus are infected with spores that, over several years, weaken and kill the colony. T. solenopsae, discovered in Brazil in 1973 and found in other areas of South America, was discovered in the United States in 1996. Scientists are studying the microsporidium as a potential biological control for fire ants in the United States. In South America, fire ant population densities are reduced in areas where T. solenopsae is found. Scientists are now studying ways to mass-produce the organism for field tests in Florida. Fire ants are thought to have spread to the United States in the 1930s and now infest 278 million acres in 11 southern states and Puerto Rico.
Center for Medical, Agricultural and Veterinary Entomology, Gainesville, FL
David Williams, (352) 374-5982

A parasitic wasp and its "partner," a virus, may help cotton growers spare innocent beneficial bugs in the battle against beet armyworms. As caterpillars, beet armyworms feed on leaves and bolls of cotton plants. They also attack soybeans, corn, vegetables and other crops. To counterattack the pests in heavily infested cotton fields, growers typically spray insecticide. But this can wipe out helpful insect predators like big- eyed bugs. These beneficial bugs could prevent minor pests from becoming greater threats and filling the niche left by deceased armyworms. ARS researchers devised a more predator-friendly approach by teaming up the armyworm's two most formidable natural enemies: a parasitic wasp called Cotesia marginiventris, and a nuclear polyhedrosis virus. Female Cotesia wasps lay eggs inside the worms; these hatch and devour the worm. The virus kills by liquefying the worm's tissues, but it is harmless to people, animals, big-eyed bugs and other beneficial insects including Cotesia. In field studies, spraying the virus onto cotton plants killed 50 percent of the worms, and releasing 500 Cotesia wasps on the 5-acre plot doomed half the survivors. All told, three-fourths of the armyworms died. More studies are planned this summer in Texas.
Biological Control and Mass Rearing Research, Mississippi State, MS
P. Glynn Tillman, (601) 323-2230

Pitting "good guy" insects against bad bugs that attack crops may sound like a simple idea, but it's not always so simple to put into action. For starters, there's the dilemma of raising sufficient numbers of the beneficial insects: What--and how--do you feed them? Now ARS scientists have developed an artificial diet for certain beneficial bugs for use in Florida's diverse agriculture. The recipe calls for liver and ground beef, plus other components that can be used to rear a variety of beneficial wasps and predators of crop pests. The ARS scientists have applied for a patent on the diet. The ARS scientists next will tackle the problem of packaging the diet. They'll work with scientists at Analytical Research Systems, Inc., of Micanopy, Florida, to test different types of polymer film coatings to contain and protect servings of the diet. The scientists want to be sure the insects can pierce the coatings and get to the food inside. In cooperation with Predation, Inc., of Alachua, Florida, ARS scientists have reared a parasitic wasp, Diapetimorpha introita, and a predator called the spined soldier bug, on the artificial diet. The main stumbling block so far: relatively low egg production from adult bugs reared on the artificial diet. The scientists are working to further refine the diet and pinpoint the cause of the low fecundity. (PATENT APPLICATION 08/692,565)
Center for Medical, Agricultural and Veterinary Entomology, Gainesville, FL
Patrick D. Greany, (352) 374-5763, pgreany@nervm.nerdc.ufl.edu

What do a natural insect virus, sugar and cottonseed oil all have in common? All are key ingredients in an experimental biopesticide that can be sprayed onto cotton plants to kill leaf-chomping beet armyworms. ARS researchers are exploring the approach as a natural alternative to conventional insecticides. Unchecked, armyworms devour the cotton plant's leaves and bolls, which produce lint, the fluffy white fiber growers harvest. In early field tests, the biopesticide killed about 60 percent of the armyworm caterpillars on cotton plants within four days. The biopesticide is made of a natural pathogen, called a nuclear polyhedrosis virus. If an armyworm swallows the virus, it destroys the insect's tissues and blood- like hemolymph. But the virus is harmless to humans, animals and beneficial insects. To ensure the worm ingests a fatal dose, the researchers use a feeding stimulant made of sugar and cottonseed oil, which the pest finds hard to resist. This summer, researchers will team with industry scientists to conduct another round of outdoor studies.
Southern Insect Management Research Laboratory, Stoneville, MS
Doug Street/Randy Bell, (601) 686-5231

A new ARS-developed lab test kit reveals if crop-destroying silverleaf whiteflies are being gobbled by beneficial bugs released into the fields. The test is a new tool in the search for effective natural alternatives to insecticides. Known as the "predator gut content immunoassay," the kit can tell if a beneficial insect has eaten even one whitefly egg. The kit deploys a team of sensitive, custom-built molecules that bind only with a specific protein found in the silverleaf whitefly. Since 1986, this whitefly has cost U.S. agriculture billions of dollars in lost crop yields and quality, insecticide expenses and related economic disruptions. The scientists aim to expand use of the "gut-check" technology. Then they can more accurately evaluate the effectiveness of releasing large numbers of lab-reared biocontrol insects to battle whiteflies and other pests.
Western Cotton Research Lab, Phoenix, AZ
James R. Hagler, (602) 379-3524, haglerj@primenet.com

Codling moth, the world's most destructive pest of pome fruits, is being controlled in the western United States through a cooperative program based on ARS technology for disrupting the pests' mating. Now in the third year of the five-year Codling Moth Areawide Suppression Program, some growers have eliminated the need for insecticide sprays. The principal method of control is mating disruption, a technology that was developed by ARS researchers. Growers place a synthetic female sex attractant, or pheromone, in dispensers that emit the chemical throughout orchards. Male codling moths, confused by the pheromone, can't find the females. The areawide program initially involved 2,800 acres. This year it has grown to include more than 10,000 acres.
Yakima Agricultural Research Laboratory, Wapato, WA
Carrol O. Calkins, (509) 454-6565, ccalkins@yarl.gov

Venom from a tiny parasitic wasp may lead to an effective biocontrol agent for agricultural insect pests that cause hundreds of millions of dollars annually in crop damage. Venom from Euplectrus comstockii stops larval growth of a variety of devastating crop pests, including cotton bollworms, tomato budworms, tobacco budworms and corn earworms. The venom is particularly useful because leaf-eating Heliothis insects are most damaging during their larval or caterpillar stage. ARS researchers have isolated and identified the active ingredient in the wasp venom. The next step is to insert the venom into an insect virus. When applied to crops, the virus will carry the venom to the pests without harming the plants. This process makes use of two biological means (the venom and the virus) to control pest insects.
Biological Control of Insects Research Lab, Columbia, MO
Thomas A. Coudron, (573) 875-5361

Last Updated: July 14, 1997
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