Effects of interactions among temperature (20, 25, and 30°c), known resistant and susceptible corn genotypes (‘Zapalote Chico’ and ‘Stowell's Evergreen’), and concentrations of corn silk material–pinto bean diet mixture (0 and 18.75, 37.5 and 67.0 mg) on corn earworm,Heliothis zea(Boddie), growth and developmental parameters were evaluated. Parameters measured were: 9-d larval weights, developmental time of larvae, weight of pupae, and days to adult eclosion. Corn earworm growth was slowest at 20°C and fastest at 30°C. Significant (P>0.05) differences caused by the resistant ‘Zapalote Chico’ compared with the susceptible ‘Stowell's Evergreen’ were measured consistently at 25°C for all four developmental parameters. The median temperature (25°C) appears to be optimum for detecting growth differences between resistant and susceptible plant materials regardless of silk concentration.