Thanks to the conscientious effort of our field scout, Ed Seymore, we have located several soybean fields in Orange County, Virginia (about 20 miles NE of Charlottesville) with large numbers of brown marmorated stink bugs. These high density areas are very much restricted to field edges next to woods, especially where there are groups of tree or heaven. On these field edges we could easily capture 10 to 20 adults and nymphs, or more, in a 15-sweep sample. The ratio of adults to nymphs was heavy on the nymph side, with evidence of old egg masses on the leaves. As best we could determine these infestations went only about 30 feet into the fields, then numbers dropped to 1 to 2, or less per 15 sweeps. There was evidence of feeding with flattened pods and discolored pods with damaged seed. There is no question that these infested areas will suffer from stay green syndrome at the end of the season. We are not sure how widespread this problem is, but are doing what we can to locate other problem areas/fields. So far, we have no other reports. In one field, we were able to put in a couple of fairly primitive insecticide efficacy trials. I use the word primitive because we had to fit plot plans into these narrow field edges with their curves and ups-and-downs (not much flat ground in that part of the state). We hope to take post treatment ratings soon and will post results, if we are successful.
Category Archives: Insect Pests
Virginia AG Pest Advisory – Dr. Ames Herbert
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.