A tiny weevil that attacks melaleuca, an invasive tree, is now thriving in at least 50 sites in south Florida. That's thanks to work by ARS researchers in Australia and Florida, who recruited the grey-brown Oxyops vitiosa weevil to stop the spread of melaleuca, also known as paper-bark tree. The scientists conducted more than a decade of tests, necessary to prove that the quarter-inch-long weevil won't attack other plants. In 1997, the scientists won regulatory approval for the first-ever outdoor releases of the weevil in America. Both melaleuca, a relative of the familiar bottle-brush plant, and the melaleuca leaf weevil are native to Australia, but neither is a pest there. In Florida, melaleuca invades an average of 14 to 15 acres every day. At one release site, the original 1997 colony of 3,300 weevils had burgeoned to about 80,000 weevils when scientists checked it again in 1999. They relocated about 20,000 of the weevils to some 30 new sites in Florida, meaning that researchers have now placed the helpful weevils in every part of melaleuca's Florida range.

Aquatic Weed Control Research Unit, Ft. Lauderdale, FL
Ted D. Center, (954) 475-0541, tcenter@ars.usda.gov
Australian Biological Control Laboratory, Indooroopilly, Australia
John A. Goolsby, 617-3214-2821, john.goolsby@brs.ento.csiro.au

A natural protein from a soil fungus may help control broadleaf weeds like yellow star thistle, dandelion, and northern joint vetch. ARS researchers discovered the protein, called Nep1, in secretions of the fungus Fusarium oxysporum. Some Fusarium strains cause crop diseases. But Nep1 plays no part in Fusarium's disease-causing machinery, scientists showed. Yet, when purified and sprayed onto weeds like dandelion, Nep1 becomes a natural herbicide. It quickly penetrates leaf openings called stomata and starts a biochemical chain reaction. This triggers the leaf's cells to commit mass suicide. Three to 24 hours later, the leaf is dead, but not the weed's apical buds, stem, or roots. Sprayed as a natural herbicide, Nep1 could help weaken a weed's dominance over crops, grasses, or other plants that normally can't compete. Nep1 mainly affects dicot (or broadleaf) weeds such as dandelion, yellow star thistle, sow thistle, and northern joint vetch. Though not intended for dicot plants like cotton, researchers speculate Nep1 could be used as a natural defoliant for easier harvesting of lint fiber. Since Nep1 is made of amino acids—a basic building block of proteins—it should be innocuous to humans and animals and break down in the environment.

Biocontrol of Plant Diseases Laboratory, Beltsville, MD
Bryan Bailey (301) 504-5325, bbailey@asrr.arsusda.gov

Some Florida vegetable growers are getting better yields in winter crops by relying on the sun instead of treatments with methyl bromide to eliminate weeds and pests. As an alternative to methyl bromide treatment, an ARS scientist enlisted several growers to test soil solarization—covering the soil under clear plastic for at least 6 weeks during summer to "cook" weed seeds, diseases and some nematodes. Before the winter crop is planted, the plastic is painted white to cool the soil enough for tender roots. In 1998, yields from solarized fields ranged from 96 to 123 percent of yields from methyl bromide-treated fields on three commercial farms. The pepper field yielding 123 percent had been deep-disked before solarization to break up stubble and bring nematodes to the surface so heat would destroy them. Two solarized pepper fields on another farm yielded 118 and 104 percent. Both had been beefed up with a biosolids compost. It was the second year of solarization for the field yielding 104 percent and the third year for the field yielding 118 percent, suggesting that solarization may gradually raise yields. Solarization saved the business of the only organic grower in the study. In his second year of solarization, production rose 30 percent, labor dropped 75 percent, and profits jumped 100 percent. But solarization has drawbacks: It works only for fall planting—half the crop in the deep South—and it doesn't adequately control all pests. Plus, growers must start preparing field beds at least 6 weeks before planting, posing logistic problems for large operations.

U.S. Horticultural Research Laboratory, Ft. Pierce, FL
Daniel O. Chellemi, 561-467-3877, dano@sunet.net

Nearly one-third of Washington's apple and pear orchards now rely on nonchemical pest management tools, thanks to a 5-year USDA-sponsored research program targeting codling moths and other pests. Washington supplies more than half of the nation's commercial apples. Young codling moths are the infamous "worms in the apple." Uncontrolled, they could destroy 80 percent of northwest apples and half the pears. ARS set up the Codling Moth Areawide Suppression Program in 1994. It relies on ARS- and university-developed technology for confusing the moths with sex attractants, or pheromones, so they cannot find a mate. This tactic is supplemented with intensive monitoring and limited pesticide spraying and relies on extensive grower participation. Previously, growers sprayed up to 6 times per year for codling moth and 4 to 6 times for leafrollers, aphids, and other secondary pests. This meant using 2 million pounds of insecticides annually at $60 to $150 per acre. With integrated pest management, or IPM, pesticide use has fallen at least 70 percent, and control is more successful. The scientists showed that using commercial insecticides can still leave 1 or 2 percent of the apples damaged by insects. With IPM, this drops to less than 1 percent and in some cases as low as 1 apple in 10,000. Mating disruption is now used on at least 60,000 acres in Washington and another 8,000 acres in California, Colorado, and Oregon. ARS' research partners include Washington State University-Pullman, Oregon State University-Corvallis, and the University of California-Berkeley.

Yakima Agricultural Research Laboratory, Wapato, WA
Carrol O. Calkins, (509) 454-6550, calkins@yarl.gov

Natural parasitic fungi could become biological controls for diamondback moths and Russian wheat aphids. The diamondback moth attacks cabbage, broccoli, canola, and other crucifers. Each year, farmers worldwide spend more than $1 billion to control it, primarily with chemical insecticides. But in many areas the moth has become resistant to conventional insecticides as well as to natural bacterial controls like Bacillus thuringiensis, or Bt. The aphid is a major pest of U.S. winter wheat and barley. Since invading the United States about 1986, the pests have cost growers more than $850 million in insecticide treatments, crop yield losses, and other expenses. ARS scientists have run laboratory and field tests that show the moth succumbs to both fungi—Beauveria bassiana and Paecilomyces fumosoroseus. But only Beauveria had a consistent impact on aphids in the field. ARS scientists and colleagues at Cornell University were the first to field-test Mycotrol, a commercial formulation of B. bassiana, against the diamondback moth. Weekly or twice-weekly applications significantly reduced insect populations and damage to seedlings, compared to chemical controls. Other scientists have shown that different strains of B. bassiana work against the Russian wheat aphid in the lab. But this is the first report of Mycotrol's field effectiveness against this aphid. Mycotrol was first developed to combat silverleaf whiteflies through a CRADA between ARS and Mycotech Corp. Butte, MT.

U.S. Plant, Soil, and Nutrition Laboratory, Ithaca, NY
John D. Vandenberg, (607) 255-2456, jdv3@cornell.edu