Characterization of Predation on Egg Masses of Ostrinia nubilalis (Lepidoptera: Pyralidae)

Abstract

Predation by several species of potential predators of Ostrinia nubilalis (Hübner) egg masses was examined under laboratory conditions to determine which species are likely predators of O. nubilalis egg masses, to characterize the damage by predators on egg masses, and to develop a technique to quantify predation on egg masses in the field. Adults and larvae of Coleomegilla maculata DeGeer, larvae of Chrysopa sp., larvae and adults of Orius insidiosus Say, adults of Stenus flavicornis Erichson, and adults of Amblyseius(?) sp. readily consumed egg masses. Adults of Hippodamia convergens Guérin, H. tredecimpunctata (L.), H. parenthesis (Say), H. variegata (Goeze), Adalia bipunctata (L.), Cycloneda munda (Say), Coccinella septempunctata L., C. transversoguttata Faldermann, C. novemnotata Herbst, and Propylea quatuordecimpunctata (L.), and neonate larvae of H. convergens, H. tredecimpunctata, A. bipunctata, C. munda, and C. septempunctata rarely consumed any part of an egg mass. Adult C. maculata consumed 1.02 egg masses/d at 24°C and 1.45 egg masses/d at 30°C, and larvae completed development from egg to adult on a pure diet of egg masses, consuming nearly 3 egg masses/d during the fourth stadium. Hatched eggs, eggs that had been preyed upon by chewing predators, eggs that had been preyed upon by Chrysopa sp., and eggs that had been preyed upon by other sucking predators could be distinguished from each other readily and reliably. Chewing predation on egg masses exposed to naturally occurring predators in maize fields at Goodhue, Minn., was correlated with C. maculata population density, and Chrysopa predation was correlated with larval Chrysopa sp. population density. Thus, characterization of predation on egg masses is a potentially useful technique for quantifying predation rates in the field.