Entomopathogenic Nematode (Heterorhabditidae and Steinernematidae) Seasonal Population Dynamics and Impact on Insect Populations in Turfgrass

Abstract

Understanding the ability of natural populations of predators, parasitoids, and pathogens to suppress prey populations is important in determining their potential as biological control agents. We measured the seasonal population dynamics of endemic entomopathogenic nematodes (Steinernema carpocapsae and Heterorhabditis bacteriphora) in turfgrass and their effect on populations of Japanese beetle, Popillia japonica, larvae and mobile arthropods associated with the soil surface and thatch layer. Both nematode species were recovered in central New Jersey in samples collected from April to December. S. carpocapsae tended to be more prevalent in the plots (32.6 and 37.1% of sections) than H. bacteriophora (8.3 and 0.3% of sections). However, when only the positive sections were analyzed H. bacteriophora had a higher density (63.6 ± 49.3 nematodes/cm2) than S. carpocapsae (17.0 ± 4.9 nematodes/cm2). Sections with H. bacteriophora had significantly lower P. japonica densities compared to sections without nematodes (58.5 ± 20.2 compared to 112.7 ± 9.2 larvae/m2). S. carpocapsae did not have a measurable impact on P. japonica populations. Mobile surface arthropods, as measured by pitfall catches, were higher in H. bacteriophora positive sections than in sections without nematodes. This difference was due to higher catches of Araneae and Lithobiomorpha. Mobile surface arthropod populations did not differ between sections with and without S. carpocapsae. The scope of H. bacteriophora′s impact on host populations is likely to be limited because of the nematodes patchy distribution.