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
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
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.