John Stommel, USDA-ARS Vegetable Laboratory, Beltsville, Maryland; phone (301) 504-5583. Corn Fungus Also Has a No-Good Cousin ARS scientists have discovered a cousin of the fungus that causes gray leaf spot of corn. This means breeders must now ensure that new corn hybrids resist both forms of Cercospora zeae-maydis. A severe infection can reduce corn yields by 25 percent or more. The fungus first turned up in this country in about 1925 in Illinois. But it didn't become a serious and widespread problem until the mid-1980s, when more and more farmers switched to tillage systems that leave crop residue on the soil surface. That's because C. zeae-maydis can overwinter in this residue. In spring, the fungus produces spores called conidia. Blown by wind or splashed by raindrops, the conidia land on leaves of newly emerged corn plants, invade, and attack the plants' tissues. The invasion may also make the plants weaker and more susceptible to infection by other pathogens. Once a problem only in the eastern part of the Corn Belt, gray leaf spot now occurs as far west as Kansas and Colorado. An ARS plant pathologist found the new form of C. zeae-maydis in the eastern part of the country. Scientists are probing its genetic makeup to learn more about its virulence. Larry D. Dunkle, USDA-ARS Crop Production and Pest Control Research Laboratory, West Lafayette, Indiana; phone (765) 494-6076. New Lure Could Take the Sting Out of Some Wasps An ARS entomologist has devised the first effective lure for the German yellowjacket, golden paper wasp, European hornet, and other yellowjackets. Commercial traps could be available in about a year. Yellowjackets and wasps are occasional nuisances for most people, but they represent an occupational hazard for fruit orchard workers during the picking season. Besides hurting, the stings can cause potentially dangerous allergic reactions. The new attractant may provide a way to monitor and control the insects. It uses compounds that bacteria and fungi make as byproducts of sugar consumption. ARS has applied for patent protection. Other baitsmade with sugar or meathave drawbacks. Sugary baits attract beneficial species, such as honey bees. As for meat, it rots too quickly to be practical in a lure. Of 17 yellowjacket species in the United States, 5 are significant, aggressive pests. The new lure is the first to attract most of them, including the German yellowjacket. It is also the first chemical lure to attract paper wasps. The scientist and Sterling International, Inc., of Veradale, Washington, are collaborating to develop a delivery system. The work is being carried out through a cooperative research and development agreement.
"Science Update" was published in the February 1999 issue of Agricultural Research magazine.