Field shldies were conducted during 1983-1986 to determine damage thresholds for western corn rootworm, Diabrotica virgifera virgifera LeConte, adults feeding on silks of inbred lines of dent corn, Zea mays L., grown under seed-production field conditions. Three inbred genotypes were used as pollen sources and three others as female plant material to assess beetle impacts. Beetle densities of one to three beetles per ear reduced kernels per hectare and kernels per kilogram, increased round kernel fractions, and decreased flat fractions for all genotypes. With simulated seed-production field conditions, effects due to distance between male pollen source and receptive female ear (row effects) did not influence beetle damage thresholds across blocks of female corn. Environmental stress and plant genotype influenced impacts of beetle density. Conditions of moishue or heat stress during pollination magnified beetle feeding effects. Abundant pollen levels also reduced impacts of beetle feeding. Regression equations for prediction of kernels per hectare as influenced by beetle density were calculated.
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Culy et al. (1992) studied this question.