COMPETITIVE INTERACTIONS BETWEEN ENTOMOPATHOGENIC NEMATODES AND BEAUVERIA-BASSIANA (DEUTEROMYCOTINA, HYPHOMYCETES) IN SOILBORNE LARVAE OF SPODOPTERA-EXIGUA (LEPIDOPTERA, NOCTUIDAE)

Laboratory experiments were conducted to assess the reproductive success of Steinernema carpocapsae (Weiser) or Heterorhabditis bacteriophora Poinar in soilborne Spodoptera exigua (Hubner) previously exposed to Beauveria bassiana (Bals.) Vuill. Treatments of H. bacteriophora plus B. bassiana resulted in higher total mortality of S. exigua in soil than treatments with either nematode alone or fungus alone. For S. carpocapsae plus B. bassiana, insect mortality was not significantly different compared with S. carpocapsae alone. In treatments with nematode plus fungus, percentage mortality of S. exigua from S. carpocapsae and H. bacteriophora was reduced relative to the treatments with with nematodes alone. These results suggest that inundative release of entomopathogenic nematodes where B. bassiana occurs may result in greater control of soilborne insect pests than application of nematodes alone.