New Aphid Threatens U.S. Soybeans

Midwestern soybean growers were caught unprepared for a visit from a foreign aphid during the summer of 2000.

Native to Asia, Aphis glycines was found in soybean fields in Illinois and neighboring states. It is not known how it came from Asia and got a foothold in the Midwest.

"A. glycines was not documented in the United States until last year and has become more of a problem in 2001 than 2000," says ARS plant pathologist Glen L. Hartman in ARS' Soybean/Maize Germplasm, Pathology, and Genetics Research Unit in Urbana, Illinois. These aphids not only devastate soybean plants by feeding on them, they also spread serious viruses, such as soybean mosaic virus (SMV)—one of the most common soybean viruses in Illinois.

Aphids are the most important and most numerous vectors of plant viruses and are responsible for significant crop losses each year. Yield losses of 60 percent have been reported when plants are infected with SMV and bean pod mottle virus.

Hartman, his ARS colleagues Leslie L. Domier and Loyd M. Wax, and scientists at the University of Illinois and Illinois Natural History Survey speculate that the soybean aphid may have been living in the Midwest for several years before becoming problematic. Mild summer temperatures last year may have spurred the increase in aphid populations.

At first, it had to be determined that these aphids were indeed soybean aphids and not cotton or melon aphids, which they closely resemble. To make that determination, ARS entomologist Manya B. Stoetzel at the Systematic Entomology Laboratory in Beltsville, Maryland, and David Voegtlin at the Illinois Natural History Survey, in Champaign, examined the aphids under a microscope to see the tiny structures that can differentiate aphids.

The researchers are studying the aphid's basic biology, attempting to monitor its movement, assessing its impact on soybean yields, determining its importance as a vector of soybean viruses, and planning potential management strategies. Chief emphasis will be given to evaluating soybean germplasm for resistance to the aphid and improving soybean resistance to SMV.—By Linda McGraw, formerly with ARS.

Glen L. Hartman is in the USDA-ARS Soybean/Maize Germplasm, Pathology, and Genetics Research Unit, 1101 West Peabody, Urbana, IL 61801; phone (217) 244-3258, fax (217) 244-7703.

"New Aphid Threatens U.S. Soybeans" was published in the May 2002 issue of Agricultural Research magazine.