Black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), larval cutting potential, development, yield losses and economic injury levels to corn in New York

The black cutworm (BCW), Agrotis ipsilon (Hufnagel), is a sporadic pest of corn in New York State. Larvae cut or tunnel seedling corn at ground level, and may cause severe yield losses. A rescue insecticide treatment is recommended if 5% or more of the plants have been cut.; Studies were conducted to provide information to assist New York farmers and pest management consultants with decisions on whether insecticide treatment or replanting is profitable, based on observed damage, crop stage, and larva maturity.; A field trial was conducted to study the impact of six increasing levels of simulated black cutworm damage on grain and silage yields. Plants were damaged at the V3 and V5 stages of corn development. The experiment was conducted on two corn hybrids, Pioneer 3921 and Pioneer 3733, planted at 6.0 and 8.0 plants m{dollar}{bsol}sp{lcub}-2{rcub}{dollar}.; A significant year effect on both grain and silage yield was detected. In both years of study, hybrid had a significant effect on whole-crop grain yield but not on silage yield, whereas plant density had no significant effect on grain and silage whole-crop yields. Significant linear and quadratic relationships between damage levels and both grain and silage yields were detected. A philologial delay associated with the damage was observed.; The effect of constant temperature and diet (artificial diet and corn) on larval development rate, growth and survival was studied. Larvae required 6 to 9 instars to complete larval development. The percentage of larvae requiring 6, 7 and 8 instars, larval development times and weight, were influenced by the diet regime, but not by temperature.; Potential damage by BCW cutting age larva, at different temperature regimes, was studied. Temperature regime and instar at infestation had no effect on the total number of plants cut by the larva from infestation to pupation.; Economic injury levels were developed, for various levels of corn and silage productivity. Calculations were made on whether an insecticide treatment or replanting was profitable, from observed damage, larva age and plant development.