Many Mississippi cotton growers are facing challenges with the high bollworm egg lays from flights of moths coming out of corn into cotton fields. The Bt toxins in corn do not work as well anymore and because cotton has similar gene trait structure, bollworms are surviving longer.
Dr. Angus Catchot, a professor of entomology and plant pathology, told the Delta FarmPress that cotton farm producers are reporting 40-50% egg lays in the South Delta area, with the areas in the north and east being hit heavy consistently. There is a correlation between the big flight of bollworms and the proximity to Bt corn crops.
Catchot has also recommended treatment based on egg threshold. In the past diamides like Prevathon and Besiege were primarily used and are now being recommended at a higher rate even though it will cost more.
Crops that are classified as VIP cotton are asked not to be treated to give those technologies a chance to work. “Although there is no recommendation to treat VIP cotton crops doesn’t make it bulletproof,” said Catchot. He also warns that the implementation of widespread VIP corn may lead to the same issue years down the road. There might be a reduction at first but it may not take long for the bollworms to develop a resistance. VIP corn is available but it doesn’t have a lot of market share.
Every bollworm comes through the corn. Decisions made in corn production will play a huge factor on cotton. It’s important for farmers to think about the selection pressure put on that gene. Cotton growers will have a more immediate problem and the corn grower will be happy for a while, even though returns may be negligible, above the other Bt traits.