PREDICTABILITY IN BIOLOGICAL-CONTROL USING ENTOMOPATHOGENIC NEMATODES

In an examination of entomopathogenic nematodes used in inundative releases on turfgrass against Japanese beetle larvae, Popillia japonica Newman, 380 treatments from 82 field trials performed from 1984 to 1988 were analyzed using a standard protocol. The results show that most test failures can be explained on the basis of unsuitable nematode strains or environmental conditions. Steinernema carpocapsae (Weiser) appears ill-adapted to parasitize Japanese beetle larvae under any range of conditions. By contrast, the HP88 strain of Heterorhabditis bacteriophora Poinar, produced on solid media, provides control comparable with that by chemical insecticides at the appropriate season (fall), soil temperature (> 20-degrees-C), soil type (silty clay), irrigation frequency (1-4-d intervals), and thatch depth (< 10 mm). The importance of multiple tests that can be analyzed is discussed. Standardized procedures are recommended for field testing; if widely adopted, they would permit comparisons between trials and the generation of large data sets needed for developing statistical models.