Spinosad, an environmentally friendly insecticide, may become a widely accepted alternative to the malathion sprays used today for battling Mediterranean fruit fly. ARS tests in Hawaiian coffee fields showed that even though malathion insecticide gave the best results in controlling medfly, spinosad and another promising malathion alternative—a red dye known as phloxine B—also gave impressive levels of control. The results also suggested that spinosad and phloxine B may need to be applied more frequently than malathion, but the total amount of active ingredient released into the environment using spinosad or phloxine B would be far less. In addition, one of medfly's important natural enemies—the tiny Fopius arisanus wasp—was significantly less susceptible to spinsosad or phloxine B than to malathion. The wasp is harmless to humans. The Hawaii tests were one of the most extensive field studies ever conducted on the effect of the three chemicals on medfly and the beneficial wasp. Medflies can attack more than 200 fruit, vegetable and nut crops and pose a constant threat to agriculture in warm-weather states such as California, Texas, and Florida. Spinosad is already approved for use on more than 100 crops, including apples, almonds, citrus, eggplant, tomatoes, and cotton.

U.S. Pacific Basin Agricultural Research Center, Hilo, HI
Roger I. Vargas, (808) 959–4329, rvargas@pbarc.ars.usda.gov

Environmentally friendly insecticides made from sugar esters could be on the market as early as the end of 2000. AVA Chemical Ventures of Portsmouth, NH, and ARS recently applied for a patent on the sugar esters—the result of an ARS concept conceived some 10 years ago. The compounds are lethal to mites and soft-bodied insects almost instantly after contact. But they do little harm to insect predators, are completely nontoxic to animals and people, and quickly degrade into harmless sugars and fatty acids in the environment. Throughout 4 years of tests, the sugar esters have been at least as effective as conventional insecticides—and sometimes more so—against mites and aphids in apple orchards; psylla in pear orchards; whiteflies, thrips, and mites on vegetables; and whiteflies on cotton. Pear psylla have become resistant even to newer insecticides, and mites are developing resistance. Like insecticidal soaps, sugar esters kill insects by either suffocating them or by dissolving the waxy coating that protects them from drying environments. Because of the way they work, insects are not expected to develop resistance any time soon. The drawbacks: The esters must come into contact with the insect to be effective, and they don't kill insect eggs.

Appalachian Fruit Research Station, Kearneysville, WV
Gary J. Puterka, (304) 725–3451 ext. 361, gputerka@afrs.ars.usda.gov

ARS research to determine a biocontrol match for mesquite in the United States has uncovered two insects that will help Australia stop the plant from spreading "down under." In the American West, balanced mesquite populations fix soil nitrogen, look great in gardens, and provide honey bees with nectar. But an overabundance causes ranchers to lose an estimated $250 to $500 million worth of water and land resources every year. A variety of natural controls keeps South America's 31 mesquite species largely in check. While searching for biocontrols that would be just as effective in the United States, researchers discovered some that would benefit other countries, including Australia. They found that two leaf-eating insects—the leaf-tier moth and the psyllid Prosopidopsylla flava—could control the spread of mesquite without harming the adult plants. The leaf-tier moth was found to be safe and effective after a 15-month quarantine study conducted by Australia's Commonwealth Scientific and Industrial Research Organization and was released. The psyllid was released after it was also found to be safe and effective.

South American Biological Control Laboratory, Buenos Aires, Argentina
Hugo A. Cordo, 54-11–662–0999, usda-ars@sabcl.ba.ar

An organic mulch made from a cover crop called hairy vetch thwarts hungry Colorado potato beetles in vegetable crops. The hairy vetch impedes beetle movement, thereby lessening their damage. This pest is notorious for its ability to develop resistance to insecticides, so biocontrol is a key option against the pest. In the study, beetle establishment occurred at a lower rate on tomatoes transplanted into hairy vetch mulch than on those transplanted into black plastic mulch. Yield of staked fresh-market tomatoes grown in hairy vetch mulch was comparable to control plots treated with insecticides. The Colorado potato beetle costs U.S. potato, tomato, and eggplant growers about $150 million annually in losses and insecticide-related costs. Noninsecticidal methods of control could be useful components of an integrated pest management strategy if they can reduce pesticide inputs, thus slowing the rate at which resistance develops.

Insect Biocontrol Laboratory, Beltsville, MD
Kevin Thorpe, (301) 504–5139, thorpe@asrr.arsusda.gov

A tiny Amazonian fly called Thrypticus that attacks waterhyacinth has for the first time been reared in large numbers. This is a crucial step toward seeing if the flies are suitable to be imported and test-released against this aquatic weed in the United States. Waterhyacinth mats infest ponds, lakes, and streams across the South and in California and Hawaii. The impacts: less drinking and irrigation water, blocked boat travel, clogged pumping stations, and damaged water quality. The mats also choke out other aquatic plants and can make a waterway uninhabitable for native fish and other animals. Natural control is essential to the weed's long-term control; herbicides and mechanical removal can be costly and ineffective. Thrypticus could become the first new insect imported to fight waterhyacinth since the 1970s. ARS researchers and colleagues discovered the new species in 1999 in the upper Amazon River basin. Immature Thrypticus flies feed within inflated stalks known as petioles that connect the leaves to the stems. The petiole is actually part of the leaf and may be up to 3 feet long and an inch thick or more. The flies' tunneling can let in microbes to further weaken or kill the plants. In December 1999, ARS researchers in Argentina released hundreds of adult Thrypticus on waterhyacinth in an outdoor cage. The flies reproduced by the thousands. Since 1996, the scientists have found 11 new South American species that attack water-hyacinth and its relatives. These include six Thrypticus, three Taosa plant hoppers, and two Megamelus plant hoppers. Researchers are screening them to identify the best biocontrol candidates. They are also making sure waterhyacinth is the only plant the insects damage.

South American Biological Control Laboratory, Buenos Aires, Argentina
Hugo A. Cordo, 54–11–4662–0999, usda-ars@Sabcl.ba.ar