Tiny proteins called peptides may help protect cotton plants from attack by Aspergillus flavus, Fusarium and other harmful fungi. ARS studies show the peptides kill certain growth stages of the fungi by forming pores in their spore walls. Once the smallest, most potent peptides are identified, scientists will engineer cotton plants with the genetic code for making the compounds to fight fungal infection. One promising candidate is Cecropin A, derived from the cecropia moth. In test-tube studies, the peptide killed 100 percent of dormant and germinating Fusarium fungi within 30 minutes exposure. It also killed many germinating spores of A. flavus. Both fungi are serious cotton pests. Fusarium can cause root rots and seedling diseases. A. flavus produces a harmful substance called aflatoxin that can contaminate cotton seed, peanuts and corn. Cotton growers typically counter these and other virulent fungi with chemical fungicides. But a more environmentally friendly approach may come from genetically engineering cotton plants that make the antifungal peptides. In addition to Cecropin A, the scientists have tested peptides from frog skin, soil-dwelling bacteria, plant seeds and other natural sources. Southern Regional Research Center, New Orleans, LA Anthony De Lucca/John Bland, (504) 286-4253, adelucca@nola.srrc.usda.gov

Future cotton-breeding lines may naturally resist Verticillium and Fusarium wilt, diseases that cost U.S. cotton producers $114 million in yield losses in 1996.ARS and Texas A&M researchers partially purified an enzyme that cancels out a natural antibiotic–desoxyhemigossypol–produced by the cotton plant. This natural antibiotic could help protect the plant against wilt disease if the enzyme didn't destroy it. The researchers are looking for a way to block production of the meddlesome enzyme. The researchers will make an antisense gene–a gene whose specific makeup is akin to a mirror image of the enzyme-forming gene. Once inserted into a cotton plant, the antisense gene should block the enzyme and therefore strengthen the plant's natural defense system against disease. Scientists hope to accomplish this within two to three years. That's good news because chemical controls for these diseases are costly and traditional breeding techniques have limited potential for further improving resistance. Southern Crops Research Laboratory, College Station, TX Robert D. Stipanovic, (409) 260-9232, rds846a@acs.tamu.edu

Two of cotton's biggest pests, cotton bollworm and tobacco budworm, remain vulnerable to the natural insecticide Bacillus thuringiensis (Bt).That finding comes from an ongoing ARS project to develop a reliable system for tracking insect resistance to Bt. In 1996-97, researchers studied 67 insect colonies (24 tobacco budworm and 43 cotton bollworm) in nine states and found those insects were only slightly more tolerant to the Bt in transgenic cotton than a highly susceptible laboratory colony. This is especially important because Bt-formulated crops are a major source of insect control. Several crops, including corn, cotton and potatoes, have been genetically engineered with the Bt gene to provide "homegrown" protection against pests. Cotton with built-in Bt is grown throughout the United States and in Australia. Several pests, including the indianmeal moth, the diamondback moth and at least nine other insects, have developed resistance to Bt, which means more chemicals must be applied to control those insects. ARS researchers plan to establish Bt resistance thresholds that would trigger remedial action. They're also working to determine the appropriate actions to take if resistance is discovered. Southern Insect Management Research Unit, Stoneville, MS Dick D. Hardee, (601) 686-5231, dhardee@ag.gov

Wasp cousins from Europe are reuniting in more areas of the northeast United States to control three native plant bugs. The alfalfa plant bug, tarnished plant bug and western tarnished plant bug are important pests of crops grown for seed in the western United States. Annually, they cost seed producers tens of millions of dollars in crop losses and controls. The toll is even higher for growers of cotton, fruit and vegetable crops pestered by the two tarnished plant bugs. Both of the beneficial wasps–Peristenus digoneutis and P. conradi–are native to Europe. A female Peristenus stings a young plant bug nymph, laying a tiny egg in it. A few days later, a wasp larva hatches and begins to eat the nymph, killing it in about a week. ARS imported both wasps about two decades ago and released them experimentally in northern New Jersey. From 1989 to the present, ARS led an interagency team to track the parasites' establishment and spread. This included surveying hundreds of fields, collecting plant bugs, and rearing and identifying parasites obtained from them. The studies determined that P. digoneutis became established in northern New Jersey by 1984 and spread to New York by 1989. Since then, scientists have found it in five additional northern states. Meanwhile, descendants of the released P. conradi wasps first turned up in Delaware in 1988. This wasp has since been found in New Jersey and New York and is likely to have spread even further. Beneficial Insects Research Laboratory, Newark, DE William H. Day, (302) 731-7330,tropp@udel.edu

U.S. haygrowers can price their crop more competitively, thanks to an ARS-developed procedure that hastens Japan's inspection and approval of compressed bales exported to that country.Japan buys about $240 million worth of U.S. hay every year to feed dairy cows, beef cattle and racehorses. But the Japanese want to keep out any Hessian flies that might lurk within the bales. Subjecting standard-size bales to 1,136 pounds of pressure per square inch compresses them to one-third their normal size. ARS scientists showed that compression alone killed 97 percent of laboratory-reared Hessian flies which were concealed–for the experiments–in bales of timothy, alfalfa, oat, bermudagrass or sudan grass hay. Fumigating bales with hydrogen phosphide for seven days at 68° F. provides an extra measure of pest control, they found. The scientists raised more than 630,000 Hessian flies for the tests. American growers started using the procedure in 1997 to capture savings in reduced storage and freight costs. Horticultural Crops Research Laboratory, Fresno, CA Victoria K. Yokoyama, (209) 453-3126,yokoyama@asrr.arsusda.gov

Last Updated: April 29, 1998
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