Joanne Whalen, Extension IPM Specialist;jwhalen@udel.edu
Soybeans
Corn earworm populations still remain low; however, with the recent increase in trap catches you will need to watch fields closely over the next few weeks.Most full season fields should be in the “bug-safe” late R6-R7 stage; however, double crop soybeans will still be susceptible to attack. Since population levels will vary from field to field, the only way to know if you have an economic level will be to scout all fields. Once pods are present, the best approach to making a decision on what threshold to use for corn earworm is to access the Corn Earworm Calculator developed at Virginia Tech (http://www.ipm.vt.edu/cew/), which estimates a threshold based on the actual treatment cost and bushel value you enter.
There are still reports of soybean aphids in an occasional field. The economic threshold for soybean aphid established in the Midwest is 250 aphids per plant. Populations should be increasing and most of the plants should be infested (>80 percent) in order to justify an application. This threshold is appropriate until plants reach mid-seed set (R5.5). Spraying at full seed set (R6) has not produced a consistent yield response in the Midwest.