https://phys.org/news/2018-10-genetic-reveals-key-resistance-global.html

Cotton, corn and soybean have been genetically engineered to produce pest-killing proteins from the widespread soil bacterium Bacillus thuringiensis, or Bt. Non-toxic to people and wildlife including bees, these environmentally friendly Bt proteins have been used in sprays by organic growers for more than 50 years and in engineered Bt crops planted by millions of farmers worldwide on a cumulative total of more than two billion acres since 1996.

Entomologists at the University of Arizona, the University of Tennessee and the Nanjing Agricultural University in China collaborated in the three-part study. Their goals were to pinpoint the mutation conferring Bt resistance in bollworms, precisely edit one bollworm gene to prove this mutation causes resistance and discover how the resistance is spreading through cotton fields in China.