University of Maryland Unlocks Mystery of Increased Corn Earworm Damage to Genetically Engineered Sweet Corn

College Park, MD -- Corn crops engineered with genes from the bacterium Bacillus thuringiensis (Bt) express specific proteins called Cry proteins, which have been a major combatant against damage from agricultural insect pests. In 2015, 81% of all corn planted was genetically engineered with Bt. Recently however, certain states have experienced increased ear damage, most notably North Carolina and Georgia, setting the stage for risk of damage to corn production across a large portion of the country. Two decades of field experiments by University of Maryland researchers have concluded that corn earworm populations are increasingly damaging to corn crops, confirming that previously effective Cry proteins expressed by genetically engineered corn are a weakened management tool.

Dr. Galen Dively, Professor Emeritus in UMD’s Entomology department predicts that corn earworm resistance to Cry proteins is likely to increase, and spread. His team’s results have broad implications for profitable corn production, biotechnology regulatory policies and sustainability of the Bt biotechnology.

Prior resistance development to Bt crops has been reported in five insect species, but all have been in response to single Cry protein expressing crops. Dively’s paper is the first report of corn earworm resistance to multiple, or pyramided Cry proteins expressed by genetically modified corn. Furthermore, this report illuminates a need for more widespread resistance monitoring for all registered Cry proteins, including the midwestern corn belt. Previously, resistance testing on corn earworm and other caterpillars has only taken place in southern production regions where Bt corn and cotton are prevalent.  

“My team is pleased to bring this information to the forefront of the farming and biotechnology industries, but recognize there is still much work to do in understanding the evolution of how corn earworm developed resistance to Cry proteins,” says Dively. “Unfortunately, with the realization of this resistance, many sweet corn farmers in Maryland have stopped growing Bt corn and by extension are applying more insecticide to combat pest infestation. Increased insecticide use is a time-consuming and hazardous long term approach which provide strong motivation to find a comparable solution to Bt biotechnology."  

Dively’s report, “Field-evolved Resistance in Corn Earworm to Cry Proteins Expressed by Transgenic Sweet Corn”, was recently accepted and published by PLOS ONE, a comprehensive academic journal featuring reports of original research from all scientific disciplines. It can be accessed here.