In conjunction with the ESA-Southeastern Branch meeting- Orlando FL, March 15, 2018
Entomologists from across the southeastern U.S. met for 2 hours at the Entomological Society of America Southeastern Branch meeting in 2018 to discuss potential resistance issues for cotton in the south due to the introduction of VIP corn expressing the VIP3a Bt toxin pyramided with Cry toxins into the region.
The group talked about potential problems that may occur with introduction of VIP3a traits in the south from a resistance management standpoint, given that we have documented resistance to both Cry1Ac and Cry2Ab already. The group further talked about many issues with compliance with current refuge strategies and adoption by southern growers.
There were many questions around compliance and ideas about increasing compliance.
Can VIP3a corn be grown in the region without threatening the longevity of VIP3a cotton various products expressing VIP3a stacked with Cry toxins)?
Are there ways to simplify refuges? Seed blends?
Can resistance be reverted? Can you increase refuge requirements or do you have to completely remove Bt corn from the system to possibly have it “revert back” to susceptibility?
Current focus of resistance management is on Cry1ac and Cry2ab. What do we need to focus more heavily on to avoid/delay resistance with VIP3a?
With resistance to the Cry proteins is VIP3a essentially a single gene in the system now?
Do we need more regulatory oversight to enforce current refuge mandates?
Many felt like the answer would be unique traits for each crop but how achievable is that in the short term?
There was a lot of discussion around what the models are saying with VIP3A saturating the market in the future in both cotton and corn simultaneously. It was brought up that resistance management success is hinging on still having some activity left with Cry2ab stacks in corn but there are issues already showing up with Cry2 toxins for CEW control.
There was a lot of discussion around why growers choose not to plant refuges. Is it threat of yield loss, ease of planting, lack of good yielding non-Bt varieties?
What about refuge in a bag (RIB) in the south? The worry is cross pollination with Bt plants. Is this worse than poor compliance? Some thought it was not.
There was a lot of discussion around introducing RIB in the south but only with non-VIP corn hybrids. The RIB would provide a refuge for corn borers, while these Cry gene hybrid fields would serve as a refuge for VIP hybrids in regard to corn earworm since corn earworm are already resistant to Cry1Ac and Cry2ab genes.
What is the possibility of having state agencies do the refuge checks? Similar to what they are doing with Dicamba.
What can this group do to help improve refuge compliance? There have also been a few incentive programs introduced in some areas. One example of success in North Carolina was approaching the discussion of refuge importance from an emotional appeal. In their pilot program, growers who planned to plant a structured corn refuge prior to the emotional appeal was 42%. After the appeal growers planning on planting a refuge went to 58%.
Discussion around making sure that state Official Variety Trials (OVT) have some conventional varieties entered by the companies. This is currently not happening much.
The group seemed unanimous that a saturation with VIP3a corn and cotton in the south would lead to resistance relatively quickly with CEW.
Most of the participants would rather not have VIP3a corn in cotton growing areas but recognized that the most elite germplasm will quickly include VIP3a corn lines forcing growers to adopt VIP3a corn in order to have the best genetics.
Angus Catchot, Mississippi State University
Jeff Gore, Mississippi State University
Don Cook, Mississippi State University
Fred Musser, Mississippi State University
Whitney Crow, Mississippi State University (Research Associate)
Tyler Towles, Mississippi State University (grad student)
John North, Mississippi State University (grad student)
Adam Whalen, Mississippi State University (grad student)
John Corbin, Mississippi State University (grad student)
Angus Catchot III, Mississippi State University (grad student)
Sebe Brown, Louisiana State University
Fangneng Huang, Louisiana State University
Jeff Davis, Louisiana State University
Gus Lorenz, University of Arkansas
Nick Bateman, University of Arkansas
Glenn Studebaker, University of Arkansas
Nicki Taillon, University of Arkansas (Research Associate)
Joe Black, University of Arkansas (grad student)
Ben Thrash, University of Arkansas (post-doc)
Aaron Cato, University of Arkansas (grad student)
Scott Stewart, University of Tennessee
Scott Graham, University of Tennessee (grad student)
Clay Perkins, University of Tennessee (grad student)
Dominic Reisig, North Carolina State University
Mohammad-Amir Aghaee, North Carolina State University (grad student)
Alejandro Del Pozo, North Carolina State University (grad student)