Influence of application method and pest population size on the field efficacy of entomopathogenic nematodes

Application method had an appreciable effect on the efficacy of Heterorhabditis sp. (isolate T390) in reducing the numbers of Otiorhynchus sulcatus infesting field-grown strawberries. Results were related to nematode placement. In Trial 1, the mean weevil mortality was 36% for trickle-irrigated Steinernema sp. (isolate NC513) at a dose of 100,000 nematodes per plant, whereas the same dose of Heterorhabditis sp. (isolate T390) resulted in mortality of 65% and 86% for trickle-irrigated and surface-sprayed nematodes, respectively. Mortality rate (y) was inversely related to initial weevil population size (x) by y = 4.96x(-0.957) and y = 4.71x(-0.558) for trickle-irrigated Steinernema sp. (isolate NC513) and Heterorhabditis sp. (isolate T390), respectively. In Trial 2, using 100,000 Heterorhabditis sp. (isolate T390) per plant, mean weevil mortalities were 61%, 63%, and 79% for single-injection, irrigation, and multiple-injection techniques, respectively.