Survival of the entomogenous nematodes Steinernema carpocapsae, S. glaseri, and Heterorhabditis bacteriophora was lower in nonsterilized soil than in sterilized soil. The nematode-parasitic fungus Hirsutella rhossiliensis was the dominant antagonist in the soil. In the nonsterilized soil, more S. glaseri than S. carpocapsae or H. bacteriophora were parasitized by H. rhossiliensis; consequently, survival of S. glaseri was lower than that of the other two nematode species. Differential survival of the three nematode species in the presence of H. rhossiliensis may be due to differences in their retention of the second-stage (J2) cuticle, susceptibility to fungal adhesion, and motility. When H. bacteriophora with and without its protective J2 cuticle was placed in H. rhossiliensis-infested soil, only 22% of the nematodes without the cuticle survived after 4 days compared with 100% survival of those possessing the cuticle. The nematode species were not equally susceptible to adhesion of H. rhossiliensis conidia. When individual nematodes contacted five conidia, fewer conidia adhered to the J3 cuticle of S. carpocapsae than to the J3 cuticle of S. glaseri or H. bacteriophora. Highly motile nematodes will encounter more H. rhossiliensis conidia than will less motile nematodes. The relative motility of the nematode species in soil was S. glaseri > H. bacteriophora > S. carpocapsae. Entomogenous nematodes that retain their J2 cuticle, exhibit low motility, and are refractory to fungal adhesion may be suitable for controlling insects in habitats with abundant parasitic fungi such as H. rhossiliensis. (C) 1991 Academic Press, Inc.
