WINTER COVER CROP SUPPRESSION PRACTICES AND NATURAL ENEMIES OF ARMYWORM (LEPIDOPTERA, NOCTUIDAE) IN NO-TILL CORN

Rye, Secale cereale L., used as a winter cover crop was killed by the herbicide paraquat or by mowing with a rotary mower. In subsequent no-till corn, Glyptapanteles militaris (Walsh) (Hymenoptera: Braconidae) and Periscepsia laevigata (Wulp) (Diptera: Tachinidae) were the most abundant of twelve species of parasitoids that emerged from field-collected larvae of the armyworm, Pseudaletia unipuncta (Haworth). No effects of cover crop suppression practices were detected for parasitism rates for any individual species or for total armyworm parasitism. Seasonal parasitism rates ranged from 32 to 45%. Higher numbers of Pterostichus spp. and Scarites spp. (Coleoptera: Carabidae), and wolf spiders (Araneae: Lycosidae) occurred early in the corn season in the mowed cover crop treatment compared with the herbicide killed cover crop treatment. Subsequent reduction of larval densities of armyworm in mowed plots following higher predator densities suggests the role of these generalist predators in biological control of armyworm.