Strong Fitness Costs of Fall Armyworm Resistance to Dual-Gene Bt Maize Are Magnified on Less-Suitable Host-Crop Cultivars

We examined the fitness costs of resistance to transgenic Cry1A.105+Cry2Ab2 Bacillus thuringiensis (Bt) maize in fall armyworm, Spodoptera frugiperda, a globally invasive pest species. Using Bt-resistant and -susceptible populations similar genetic backgrounds, we compared insect life-history traits population growth rates on foliage Bt or non-Bt cultivars maize, soybean, cotton. found that (i) alleles led major reduction seven eight three host crops studied; (ii) developmental time was trait accounted for most variation (iii) magnitude resistant individuals stronger cotton foliage, which insects did not pass subsequent generations. These results show armyworm Cry1A.105+Cry2Ab2-expressing comes with strong costs, were magnified less-suitable plants insects. Thus, natural selection may help maintain even restore susceptibility pesticidal proteins perhaps is significant factor helping manage maize. findings indicate multi-toxin can be strong, conditions magnify differential susceptible could specifically deployed refuge improve management crops.