Tuesday, November 6, 2007
159-2
A Case for the Presence of Soybean Aphid Biotypes in Michigan.
Clarice Mensah, Christina DiFonzo, and Dechun Wang. Michigan State University, 286 Plant And Soil Science Blding, East Lansing, MI 48824
The soybean aphid (Aphis glycines Matsumura) has over the past five years become one of the most important pests of soybean [Glycine max (L.) Merr.]. There is no documentation of the existence of biotypes of soybean aphids in the USA . However in other aphid species, like the green bug and Russian wheat aphid biotypes have arisen in response to the release of aphid resistant genotypes. With the testing of several soybean aphid resistant genotypes it is only a matter of time that biotypes which would overcome aphid resistance would evolve. In a field study in 2006, Dowling a resistant check was found to be susceptible in one of three replications. A greenhouse study was conducted to compare the effect of the aphids which overcame the resistance in Dowling and aphids in replications where Dowling was still resistant. Dowling was found to be susceptible to both aphid colonies. This year another greenhouse study was conducted using aphid colonies which have been raised in a growth chamber and greenhouse since 2002, Dowling was found to be resistant. These two greenhouse results clearly indicate a difference in the feeding behavior on Dowling by aphids collected in 2002 and 2006 and suggests that biotypes have evolved in soybean aphids in Michigan .