By Jessica Domel
Multimedia Reporter
Entomologists urge Texas cotton farmers to scout their cotton and take action when necessary to protect the crop from a growing number of biotech (BT)-resistant bollworms.
It’s unclear whether or not farmers will see increased bollworm pressure, but the potential is there, according to Dr. David Kerns, entomologist for Texas A&M AgriLife Extension and statewide integrated pest management coordinator.
“I will say there’s already populations being picked up in some of the native hosts. As far as overall pressure, we just don’t know,” Kerns said in an interview with the Texas Farm Bureau (TFB) Radio Network. “The real problem we’ve been facing, though, is issues with BT resistance in these populations.”
Kerns leads a research project with the Cotton Technology Stewardship Committee, which is comprised of seed companies and others with vested interests in cotton.
The project involves collecting worms from damaged crops, including cotton, establishing colonies in a lab and running assays to determine how they respond to varying levels of BT toxins in their diet.
“One hundred percent of the populations we evaluated were resistant to the original BT, the Cry1Ac. Probably 70-80 percent of them were resistant to the newer one, the Cry2Ac toxin. They’re all resistant to the Cry1F, as well,” Kerns said. “The only BT toxin we haven’t picked up any resistance in is for the VIP BT toxin.”
The problem is the BT toxins used in cotton are also used in one form or another in corn varieties.
“That’s just that much more selection pressure on these toxins,” Kerns said.
An increase in corn acreage with the VIP3A toxin could also lead to bollworm resistance to that toxin.
In the meantime, the committee continues to study bollworm populations for answers.
“We’re going to try to measure how common the resistance genes are in the environment. That would be the newer part of the study,” Kerns said.
Farmers are encouraged to scout their fields often and treat when necessary. For those who have not yet selected their seed, Kerns encourages picking a variety that will have the best yield for the area.
“It doesn’t matter what the BT technology is, you’ve got to have something that’s going to perform on your farm. Then, you need to know the risks associated with what you pick,” Kerns said. “If it is something that doesn’t contain the VIP gene, then they may have issues with bollworms and just need to be very cognizant of it.”
VIP3A is not a silver bullet to resisting bollworm damage. Stressed cotton may not express enough VIP3A to provide the desired control.
“Those trying to ride this VIP technology exclusively to protect their crop from bollworms are setting their crop up for a very dangerous scenario,” Kerns said. “That’s just bad management. Producers should pick their cotton varieties based on something that’s going to yield on their farm.”
If bollworms are spotted in cotton, Kerns urges farmers to treat the field before the pests get too big.
“If you allow bollworms to get very big and they move into the plant’s leaf canopy, you won’t get them even using this very good chemistry, because you won’t be able to get the product down there where they are feeding,” Kerns said. “Timeliness is of the utmost importance. We have a lot of producers who say: ‘Well, I’m going to wait to see if the technology works,’ after seeing a lot of small worms. They wait too long and then they’re unable to control them.”
Kerns is also working with the U.S. Department of Agriculture, University of West Georgia and North Carolina State University on a similar project relating to BT resistance in bollworms. They’re studying the frequency of the genes in the environment.
“We can maybe use that to predict the sustainability of the BT toxins,” Kerns said.
The first instances of bollworms resistant to BT technology in cotton were noted in 2010.