Cultivation of transgenic crops engineered to produce insecticidal proteins from Bacillus thuringiensis (Bt) has grown rapidly in the past 25 years. Bt crops have had noteworthy successes, but resistance to Bt crops has evolved in numerous instances. Five cases of practical resistance to Bt proteins that are produced by transgenic crops are documented for corn earworm (Helicoverpa zea), which is the most for any pest. (Photo by John C. French Sr., Retired, Universities:Auburn, GA, Clemson and U of MO, Bugwood.org)