Cotton Consultant's Corner:
BS degree in Agricultural Entomology – Mississippi State University
In cotton, we are not allowed to spray for lepidopteran pests on the five percent unsprayed option refuge acres. You have to let these pests reproduce and, hopefully, to breed out the possibility of resistance through cross mating.
Mississippi is now in the eligible region where we can choose to go with the natural refuge option for Bollgard II cotton, which would be one of the benefits of planting these varieties. That takes away the worrisome decision of whether to choose the five percent or 20 percent refuge. It’s been proven that there are plenty of wild hosts out there to supply enough Heliothis virescens to infiltrate the population, breed with them and delay resistance.
If we plant the current YieldGard corn, we have to plant 50 percent of the acres in Bt and 50 percent non-Bt to serve as refuge acres to hopefully delay resistance. In the Bt corn, we don’t have to deal with corn borers. That pest is effectively controlled. Unlike the five percent unsprayed option in cotton, we can spray the non-Bt hybrids for corn borers.
Now the YieldGard VT Triple PRO corn hybrids have an additional gene, which will give better control on the European and Southwestern corn borer and also control the corn earworm and fall armyworm. The Bt hybrids we currently have control some of the corn earworms, but very few of them.
Although we haven’t had many corn earworms last year and this year, I don’t think it will stay that way. Because there is a possibility of reducing the refuge requirements in corn, then down the road YieldGard VT Triple PRO will be what everyone wants to plant.