(Photo by Casey Kuhn - KJZZ)

Cotton crops in Arizona.

After 11 years of study, a University of Arizona researcher has discovered a new way to reverse the spread of a destructive cotton pest. 

Scientists genetically engineered a type of cotton that kills pink bollworms, which can wipe out the crop. But, if a grower only farms that type, the pests able to resist those measures breed and make more resistant bugs.

That’s what happened to Chinese cotton farmers, until they started planting a new type of hybrid cotton.

UA Head of Entomology Bruce Tabashnik led the study that discovered the hybrid reverses bollworms resistance, and says it was an unintended consequence of planting that strain.

“The remarkable thing is this resistance reversal was kind of an accident," he explained, "Kind of a side benefit.”

The Chinese farmers had originally planted the hybrid because it had traits that were more desirable, like increased crop yield. What this discovery shows is how that hybrid, which combines the GMO and conventional cotton strains, also displays the different pest-resistant strains: some grow as resistant to the bollworm, while others grow non-resistant. That randomization reverses the spread of the pink bollworms resistant to that GMO strain. 

Tabashnik says planting cotton hybrids could now be an option for American cotton farmers.

The study looked at 66,000 different bollworm caterpillars to find how the hybrid plants reduced the resistant bugs.

“The hybrid part of what’s going on in China is not happening in the U.S. but it’s possible that it could be investigated and potentially employed in the U.S. as well,” Tabashnik said.

Arizona cotton farmers currently avoid resistant bugs by planting a regulated mixture of GMO cotton and conventional cotton seed in their fields.