Resistance for corn earworm could be high in some locations says data from Ames Herbert Virginia Tech Extension Entomologist. Herbert says a resistant population is indicated at anything from 30% survivorship to 50% survivorship and his vial assay data confirms up to 50% survivorship in some locations in tests this season, "about as high as we have seen it," he says.
The information comes from Tim Britton, an ag Extension agent in Johnston County, North Carolina, in his weekly "Johnston County Ag Report.
Herbert also notes that beet armyworm numbers are increasing in some areas of both North Carolina and Virginia and that these caterpillars are tolerant to pyrethroids.
Corn Earworm, Stink Bugs, Pose Problems For Cotton and Soybean Growers
"Consider applying Belt, Steward, or Blackhawk (the new name for Tracer) for corn earworm," Herbert says. "If you have stink bugs and are in the R4-R6 stages, you might want to tank mix one of these products with a pyrethroids. If you do apply a pyrethroid first for corn earworm, do not follow this spray with another pyrethroid for worms.
Britton also notes reports of small corn earworm (sorghum headworm) larvae in sorghum heads. Britton recommends sampling once growers have heads in sorghum.
As cotton fields in most areas in the Carolina-Virginia region are in or are approaching their third to fifth week of bloom, there are also numerous reports for stink bugs in cotton and soybeans. Cotton entomologist Jack Bacheler, NCSU, notes it indicates we are in the midst of a big year for stink bugs. He has a blog article hosted by NCSU that tells growers what chemicals they should consider fighting stinkbugs that are "pounding cotton." It can be found at http://www.nccrops.com/2012/07/26/stink-bug-pounding-cotton-what-to-spray/.
Be sure to see our insect roundup article for the Carolina-Virginia region in the September issue of Carolina-Virginia Farmer magazine. It will discuss these issues in more depth and also look at the threats other insect pests pose for the region.