Determining pest and pesticide interactions as a means to optimize soybean yield

Soybean cyst nematode (SCN) and soybean aphid (SBA) are serious pests of soybean.  Farmers have to scout fields regularly and apply foliar insecticides to protect yield from SBA.  Yield loss from SCN can be high in dry seasons and when population densities are high.  Farmers can grow soybean varieties with native host plant resistance for SBA, SCN or both.  While these varieties do not kill the pests, they reduce pest reproduction and subsequently reduce damage.  Seed treatments for soybean can provide additional crop protection from pathogens, nematodes and insects.  For our field experiment, we will study pest reproduction and soybean yield for varieties with resistance to SBA, SCN or both pests, as well as for a variety that is susceptible to both pests.  We also will test seed treatments and foliar applications of insecticide for SBA.  The field study will be performed at two different locations in Iowa for three field seasons to determine which integrated pest management practices best preserve soybean yields and keep pests at bay.  We hypothesize that the soybean varieties with host plant resistance for both SBA and SCN and with a seed treatment will have greater yield than susceptible varieties and soybeans without the seed treatments.  Results from the first season of the field study will be presented.