none Computer simulations were used to evaluate the impact of tillage upon black cutworm, Agrotis ipsilon (Hufnagel), damage to seedling corn through its effects on cutworm infestation, feeding and parasitism by Meteorus rubens (Nees von ESenbeck). Using 1982 conditions of Urbana, Illinois, simulated black cutworm infestations in no-till fields approached the economic threshold of two larvae per 100 corn seedlings. In disked and conventionally tilled fields, infestations were 30 and 57% less, respectively, because weeds for oviposition sites were less abundant before planting. Simulations suggest that M. rubens - weed interactions are of minor importance compared to black cutworm - weed interactions in influencing cutworm damage. In addition, they indicate that preferential cutworm feeding on weeds can substantially offset preferential cutworm oviposition in weedy, reduced-tillage fields. Animals and man; Habitat modification; Techniques; Ecological techniques; Nutrition; Diet; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts Agrotis ipsilon (Noctuidae); Agricultural activity; Tillage effect on interaction with hymenopteran parasite; Ecological modelling; Interactions with hymenopteran parasite & weeds; Food plants; Weeds, effect of tillage & hymenopteran parasite; Hymenopteran parasites; Meteorus rubens; Interactions, simulation model; Host parasite relationships; Interactions with Meteorus rubens (Hymenoptera), tillage effects, model Meteorus rubens (Braconidae); Agricultural activity; Tillage effect on interaction with lepidopteran host; Ecological modelling; Interactions with lepidopteran host; Lepidopteran hosts; Agrotis ipsilon; Interactions, simulation model; Host parasite relationships; Interactions with Agrotis ipsilon (Lepidoptera), tillage effects, model