I have looked at a few fields of Soybeans today and some of them have treatable levels of Soybean foliage feeders (mostly Soybean Loopers) in them. We have two different ways of determining whether a spray is needed on soybean foliage feeders. This can be done either using insect counts (gathered using sweep nets or drop cloths) or by using the percent defoliation method. The thresholds for both methods are shown below.
Growers who have reached a treatable level of foliage feeders in their soybeans, need to be sure to determine which species of foliage feeders are present in their field before making an application. Some species of foliage feeders are highly resistant to pyrethroid insecticides and growers will not achieve good results if they do not select the proper insecticide.
The list of insecticides labeled for foliage feeding caterpillars in soybeans can be found in the 2014 Georgia Pest Management Handbook on pages 495-500, or at http://www.ent.uga.edu/pmh/Comm-Soybeans.pdf .
Terminating Insecticide Applications
While most of our soybeans are still several weeks away from reaching maturity, some of the early-planted soybeans may be nearing the time when we should consider terminating insecticide treatments. Growers can terminate insecticide applications when their soybeans have reached the R7 growth stage and are relatively insect pest free. The R7 growth stage is when at least one pod can be found on the plant that is mature (turning brown or tan).
If you have any questions about treating foliage feeders in soybeans, contact your local extension agent for more information.