Corn earworm moths are beginning to migrate from corn fields and levels of pyrethroid survivorship are extremely high (see other advisory posted on July 28). Corn earworm populations are always worse in dry years. But we have had some recent rains over much of Virginia so we may see some benefit from those. Corn earworm moths are already laying eggs in cotton, so likely they are also laying eggs in soybean fields. They would be attracted to flowering fields and those with younger pods. A lot of our crop is in these growth stages. I would recommend beginning to scout soybean fields by next week in the southern counties, and by the middle of the following week in middle and northern counties. How will this problem develop over the next few weeks, only time will tell?
Although stink bugs are present in some soybean fields, the numbers are still low. We are seeing a shift from primarily brown stink bugs to primarily green stink bugs, which is the norm for this time of year in Virginia. Fortunately, green stink bugs are easy to control with pyrethroids, and when browns comprise 30% or less of the total (which is the norm), we also see good control. Although brown marmorated stink bugs are being reported in some locations in Virginia, so far, none have invaded soybeans, and this is also true for Maryland. We will begin a large scale soybean monitoring effort next week (Aug 1).
What are our current recommendations for controlling soybean insects? Because of the potential for corn earworm pyrethroid resistance/tolerance, consider a non-pyrethroid insecticide option, especially if worm counts are high (more than 3 times the threshold). If stink bugs are also present in economic levels, a pyrethroid or neonicotinoid insecticide would need to be added as most of the non-pyrethroid worm control options do not provide stink bug control. Another option that has a good track record both here and in the Delta states is a tank mix of one-half pound of Orthene (Acephate) plus a high rate of pyrethroid. For reasons we don’t fully understand, this tank mix is doing a very good job in controlling corn earworms, tobacco budworms, and stink bugs.