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Cumulative number of species of cotton pests with documented field-evolved resistance to Bt cotton or DDT in years following their introduction in the US. Data on evolution of resistance to DDT are from APRD (2009). Some species categorized as evolving resistance to DDT between 1946 and 1963 in APRD (2009) were not included in the Figure (Lygus hesperus and Spodoptera exigua) because primary literature stated that populations tested for DDT resistance had not been collected in cotton.
