Genetically Engineered Bt Corn and Range Expansion of the Western Bean Cutworm (Lepidoptera: Noctuidae) in the United States: A Response to Greenpeace Germany

The western bean cutworm, Striacosta albicosta (Smith), is a pest of corn and dry beans in North America. Before the late 1990s, economic infestations of the insect were restricted mostly to the western Great Plains and Idaho. During 1999-2009, it greatly expanded its range and moved across the central and eastern regions of the Corn Belt, eventually reaching northeastern Atlantic coast states. Greenpeace Germany issued a 2010 report claiming that the dramatic range expansion of the western bean cutworm was due entirely to "pest replacement" that resulted from the adoption of genetically engineered Bt corn, which suppressed one pest species and allowed another species-the western bean cutworm, in this case-to take its place. We maintain that the scientific literature does not provide empirical field-collected data to support the Greenpeace Germany claim that Bt corn is the sole factor that influenced the range expansion of the western bean cutworm. We propose broader ecological and agronomic factors to explain why the western bean cutworm has recently expanded its geographic range to include all of the major corn-growing areas in the central and eastern United States. These additional factors may include insect biology, insect and corn phenology synchrony, reduced insecticide use, conservation tillage, soil type, glyphosate-resistant crops, insect genetics, insect pathogens, preexisting insect population densities, and climate change.