Infective juveniles of the entomopathogenic nematode Heterorhabditis bacteriophora exposed to medium-wave ultraviolet radiation (302 nm) were inactivated at radiation levels that did not affect Steinernema carpocapsae. Irradiated H. bacteriophora showed a significant delay in progeny emergence at an exposure of 1.5 min, a decline in reproductive capacity at 2 min, and loss of pathogenicity at 4 min. Negative effects were not noted until exposures of at least 6 min for S. carpocapsae. Complete inactivation of H. bacteriophora resulted following 4 min of irradiation, compared with 10 min for S. carpocapsae. The infective juvenile sheath, an additional cuticle retained from the second-stage molt, did not provide either nematode species with significant protection from uv inactivation. The poor uv stability shown by H. bacteriophora is consistent with the tendency of heterorhabditids to be less tolerant of environmental stress than steinernematids. Heterorhabditid nematodes appear to be among the most vulnerable of all entomopathogens to uv inactivation. Their application onto exposed surfaces such as foliage should be discouraged.
All Science Journal Classification (ASJC) codes
- Ecology, Evolution, Behavior and Systematics
- Heterorhabditis bacteriophora
- Steinernema carpocapsae
- biological control