We have been experiencing a high level of bollworm activity in Arkansas soybeans.
Numbers continue to increase and we have observed and had reports on numbers as high as 75 bollworms per 25 sweeps. We have seen many fields at levels from 25 to 40 per 25 sweeps.
As this situation has spread across the state we are beginning to see less than adequate control with pyrethroids such as Karate, Mustang Max, Brigade, etc.
This situation was first observed in Louisiana and Mississippi and now we are beginning to see where applications are not cleaning up infestations of bollworms and in several cases failing to reduce numbers below threshold. In some cases, application may be a factor but, certainly, when the number of failures increases dramatically other factors may be involved.
Here are some recommendations for treating bollworms, particularly in high infestation level situations:
Application volume of 5 gallons per acre by air and 10 gallons per acre by ground.
Add a surfactant or crop oil. With the high heat we are experiencing this may help get the material down in the canopy.
In high infestations (2X threshold), tankmix pyrethroid with 0.5 pound acephate to improve control.
Remember, when sampling for bollworm you have to “get in there” and dig them out. Sweep deep in the canopy and make visual observations of the plant as you go. Many people are underestimating the bollworm population due to poor sampling technique.