Update on corn earworm and brown marmorated stink bug in the Virginia soybean crop.
The corn earworm pyrethroid vial test data are showing some decline in the percent surviving…which is good. But levels are still high enough to indicate possible control problems. As I said in last weeks advisory, I think high rates of pyrethroids will work well enough in soybean fields with threshold or just above numbers of worms. If we get into a situation like last year with high numbers (e.g., 15, 20, 30 or more per 15 sweeps) then misses are much more likely and non-pyrethroids would be needed to achieve good control. In general, the non-pyrethroids will not do a good job of controlling stink bugs so if they are also present, pyrethroids, which do a good job on stink bugs, would need to be tank-mixed. The CEW moth flight from corn seems to be a little slow in developing. Our traps are catching an average of about 60-70 per night, but elsewhere in the state counts are still pretty low. As far as we can determine, no worms have been found yet in any soybean fields in Virginia. We expect to find some in the southeastern part of the state by next week. It is a bit too early to speculate, but we may have a much easier year this year with fewer infested fields compared with previous years. Our survey for brown marmorated stink bugs started this week and we found them in several soybean fields (Orange and Fauquier Cos.). But they were very scattered in fields and in low numbers (well below 1 per 15 sweeps). We found both adults and nymphs and in one field, egg masses. Delaware reports seeing low numbers in most soybean fields, and I suspect, as we progress with our survey, we will find the same thing. So far, these very low numbers do not represent any threat to the crop. How will this evolve? My best guess is that as populations increase and begin to move from other plant hosts, we may see larger numbers build up toward the end of the season, especially in our double-crop fields.