Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Soybeans
Be sure to sample the earliest planted fields for bean leaf beetles, potato leafhoppers, thrips, grasshoppers, green cloverworm and spider mites. Grasshoppers are present, especially in no-till fields. As soon as the weather turns hot and sunny we could see a significant increase in activity. As barley and wheat are harvested and soybeans are planted, these fields will be susceptible to attack and grasshopper feeding can often cause stand loss. If stand reductions are occurring from plant emergence to the second trifoliate, a treatment should be applied. Although no precise thresholds are available, a treatment may be needed if you find one grasshopper per sweep and 30% defoliation from plant emergence through the pre-bloom stage. Numerous products are labeled for grasshopper control in soybeans. Be sure to check all labels carefully before combining insecticides and herbicides since there are a number of restrictions, including cautions on phytotoxicity.
By now, all should also be aware of another potential soybean insect pest, the Kudzu bug. It was not found in Delaware surveys in 2012; however, it has been found in a larger geographic area in Virginia already this season. This pest can cause significant yield loss. The good news is that the southern region entomologists have done an excellent job of developing effective sampling and decision making guidelines. Please refer to the following link for pictures of adults and nymphs as well as management strategies http://www.kudzubug.org/index.html.