Consumption and Utilization of Three Maize Genotypes by the Southern Armyworm12

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Abstract
Maize varieties with different mechanisms of leaf-feeding resistance to the European corn borer, Ostrinia nubilalis (Hübner), were evaluated for resistance to feeding of the southern armyworm. Spodoptera eridania (Cramer). Armyworm feeding bioassays were conducted with the U.S. inbred, B49, which has high tissue concentrations of DIMBOA [2,4-dihydroxy-7-methoxy(2H)-1,4-benzoxazin (4H) one] and a Caribbean genotype (San Juan × Antigua, with mechanisms of borer leaf-feeding resistance different than the DIMBOA type) in comparison with borer-susceptible DIMBOA-less mutant (bxbx). Metabolic costs of penultimate-instar armyworms fed B49 and SJ exceeded 80% of the assimilated biomass; however, increased consumption rates on these borer-resistant genotypes permitted armyworm growth rates much greater than expected. High consumption rates and a recovery in the subsequent final-instar conversion efficiencies actually resulted in more rapid armyworm growth rates on B49 and SJ maize. Such versatility in feeding and detoxification abilities of this polyphagous species is certainly a major reason for the lack of success in developing armyworm-resistant plants.