Resistance of the fall armyworm,Spodoptera frugiperda, to transgenicBacillus thuringiensisCry1F corn in the Americas: lessons and implications for Bt corn IRM in China

The fall armyworm,Spodoptera frugiperda(J.E. Smith), is a major target pest of Bt crops (e.g., corn, cotton, and soybean) in North and South America. This pest has recently invaded Africa and Asia including China and the invasion has placed a great threat to the food security in many countries of these two continents. Due to the extensive use of Bt crops, practical resistance ofS. frugiperdato Cry1F corn (TC 1507) with field control problems has widely occurred in Puerto Rico, Brazil, Argentina, and the mainland United States. Analyzing data generated from decade-long studies showed that several factors might have contributed to the wide development of the resistance. These factors include (1) limited modes of action of Bt proteins used in Bt crops; (2) cross-resistance among Cry1 proteins; (3) use of nonhigh dose Bt crop traits; (4) that the resistance is complete on Bt corn plants; (5) abundant in initial Cry1F resistance alleles; and (6) lack of fitness costs/recessive fitness costs of the resistance. The long-term use of Bt crop technology in the Americas suggests that Bt corn can be an effective tool for controllingS. frugiperdain China. IRM programs for Bt corn in China should be as simple as possible to be easily adopted by small-scale growers. The following aspects may be considered in its Bt corn IRM programs: (1) use of only high dose traits for bothS. frugiperdaand stalk borers; (2) developing and implementing a combined resistance monitoring program; (3) use gene pyramiding as a primary IRM strategy; and (4) if possible, Bt corn may not be planted in the areas whereS. frugiperdaoverwinters. Lessons and experience gained from the global long-term use of Bt crops should have values in improving IRM programs in the Americas, as well as for a sustainable use of Bt corn technology in China.

Automated summary

The fall armyworm, a major pest of Bt crops in North and South America, has recently invaded Africa and Asia, including China, posing a threat to food security. The resistance of S. frugiperda to Cry1F corn has been widely observed in Puerto Rico, Brazil, Argentina, and the United States due to various factors such as limited modes of action and cross-resistance among Bt proteins. Strategies for integrated resistance management in China include using high dose traits, monitoring resistance, employing gene pyramiding, and avoiding planting Bt corn in areas where armyworms overwinter. Lessons from global Bt crop use can be valuable for improving resistance management programs in the Americas and promoting sustainable Bt corn technology in China.