By Ames Herbert, Virginia Extension Entomologist
With a full complement of field scouts in place, more soybean fields are being found with brown marmorated stink bug infestations.
We are up to 20 counties in Virginia spread over a very large area of the state.
Infestations were a little slow to develop compared with last year, but we are predicting that by the end of the season, many more fields will be infested compared with last year.
So far, most infestations are at low to moderate levels (from 2-3 to 4-6 per 15 sweeps) but a few are in the high infestation range 8-10 or more/15 sweeps.
We know that sweep netting is not the ideal way to sample for these insects, but there is no other method other than simply easing into the field edge and counting what you see. Basically, if you can stand in one spot, do a 360 degree turn and count more than 5 or 6, that area needs protection.
So, how are they not playing by the rules? Last season, our first with treatable levels, bugs stayed on field edges and a single insecticide edge treatment provided season long control. This is true for many fields this year, but in a few we are finding them deeper into fields, and, there are some cases where re-infestations are occurring in fields previously treated.
The good news is that 1.) based on our insecticide trials it is not difficult to kill them with several common products, and 2.) many fields, especially the full-season crop fields, are rapidly approaching the safe stage, which based on previous field cage studies happens after R6 (full seed) when pod walls begin to toughen.
Many growers are treating field edges this year and we are going to follow as many as possible to determine if those treatments worked and held. More on this as we progress.