none Observational studies were conducted in 1995 and 1996 to sample natural enemies of the European corn borer, Ostrinia nubilalis (Hubner) (Lepidoptera: Pyralidae) along field borders with differing vegetation levels. Corn fields adjacent to three broad classes of border vegetation: herbaceous, intermediate, and wooded, were studied. A cornfield adjacent to each border class was sampled along the entire length of its respective border. Ostrinia nubilalis larvae collected were evaluated for presence of the entomopathogens Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) and Nosema pyrausta (Paillot) (Microspora: Nosematidae) and the parasitoid Macrocentrus grandii Goidanich (Hymenoptera: Braconidae). There was a negative interaction noted between larvae parasitized by M. grandii and O. nubilalis larvae infected with N. pyrausta. This antagonism between the two biotic factors may explain why increased food and shelter adjacent to corn bordering diverse vegetation did not result in significantly higher parasitism in limited observations. The levels of entomopathogen infections also were not consistently influenced by border vegetation type. Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Diseases and disorders; Diseases; Microbial diseases; Habitat; Man made habitat; Land and freshwater zones; Nearctic region; North America; USA Nosema pyrausta (Microspora ); Macrocentrus grandii (Braconidae ); Lepidopteran hosts; Ostrinia nubilalis; Prevalence; Iowa; Polk & Story Counties; Prevalence in lepidopteran hosts, field border vegetation relationship Ostrinia nubilalis (Pyralidae); Hymenopteran parasites; Macrocentrus grandii; Protozoan parasites; Nosema pyrausta; Fungal diseases; Beauveria bassiana; Cultivated land habitat; Iowa; Polk & Story Counties; Parasite & fungal disease prevalence, field border vegetation relationship