PARASITES ASSOCIATED WITH LEPIDOPTEROUS PESTS OF ALFALFA IN OKLAHOMA

Scope and Method of Study. Lepidopterous pests in Oklahoma alfalfa (Medicago sativa L.) fields were collected from two unsprayed sampling areas (Chickasha and Stillwater) at weekly intervals. Also, statewide surveys were conducted at monthly intervals to determine seasonal incidence and abundance of hosts and parasites associated with each. Larvae were reared individually on artificial diet or alfalfa bouquets until host or parasite emergence, after which identifications were made and a parasite reference collection was established to aid in future parasite indentifications.;Eight species comprised the "foliage feeder" complex. All have the same general feeding habits and were present throughout the alfalfa growing season. The three most common pests in this group were Heliothis zea (Boddie), Colias eurytheme (Boisduval), and Plathypena scabra (F.). Damaging populations of any one of the eight species were uncommon, but when several were present, noticeable defoliation often occurred. Microplitis croceipes Cresson was the important parasite of H. zea. Common parasites associated with C. eurytheme were Apanteles flaviconchae Riley and Chetogena "claripennis Macquart". Rogas nolophanae Ashmead and C. "claripennis Macquart" were most often associated with P. scabra. Frequently, a parasitic species attacked several species of the foliage feeder complex with potential for reducing crop damage by these pests. These natural enemies help in regulating host populations below the economic threshold.;Findings and Conclusions. A total of 10 species of lepidopterous larvae were collected. Euxoa auxiliaris (Grote) and Peridroma saucia (Hubner) were present only in spring and caused damage in a relatively low number of the fields sampled. The most abundant parasites associated with E. auxiliaris were Meteorus leviventris (Wesmael) and Apanteles griffini Viereck. Species most frequently parasitizing P. saucia were Peleteria texensis Curran and Archytas apicifer (Walker).