Our new Extension Grains Agronomist, Corey Bryant let us know that he is getting calls about stink bugs in corn. Here are a few comments from him on their signifigance and how to manage them:
The critical period for stink bug control is during the ear formation period, approximately V12 – VT. Stink bug feeding on developing ears will cause them to emerge deformed and not develop properly or completely fail. If damaged ears do develop they may also be more susceptible to disease. Once the ear has emerged and begun silking, feeding damage on the ear is limited to the individual kernel. This is not to say that we should stop scouting but that feeding damage will not injure the entire ear at this point.
The only way to identify stink bug infestations is through timely and proper scouting. Current thresholds are 1 stink bug per 4 plants during the ear elongation/vegetative tasseling stage, and 1 stink bug per 2 plants during the silking/pollination and blister growth stages, R1 – R2. These do not have to be all in a row or within a specified section of row. For instance, if you look at 8 plants randomly in a field and 2 of those plants have stink bugs on them you have reached threshold if the corn is in the V12 – VT growth stage. If the corn is in the R1-R2 growth stage you would need to find stink bugs on 4 of the 8 plants you looked at to reach threshold.
If you scout a field and find you have reached threshold then pesticide choices should be based on the prevalent stink bug species in the field. Pyrethroids are effective against green and southern green stink bugs but not brown stink bugs. If your infestation is predominately brown stink bugs then the grower will need to apply a full rate of Bifenthrin, 0.1 lbs ai/acre. It may be necessary to make multiple applications during the season as well, so just because you made one application for control do not assume you are free and clear. Fields that border wheat or other small grain fields are more susceptible to infestations as stink bugs begin to move out of the mature and harvested fields and into actively growing corn.