Photo credit: Scot Nelson

A study published in the journal PLOS ONE has found that one of the worst insect pests to attack corn and cotton, the corn worm (also commonly referred to as the earworm or bollworm), has evolved resistance to genetically modified crops that express multiple insecticidal toxins from the bacterium Bacillus thuringiensis (Bt). Researchers used over 20 years of field observations in addition to laboratory experiments to assess the earworm’s resistance to the BT corn.  They found that strains of the earworm that had evolved resistance to the multiple insecticidal traits expressed by the corn hatched faster, gained more weight and were significantly more likely to survive to adulthood than strains of the earworm that were still susceptible to the GMO corn. Through communication with growers, the authors also found that farmers still growing the GMO corn are compensating for pest resistance by increasing their pesticide applications. The authors predict that corn worm resistance is likely to increase and spread.