Efficacy of the entomopathogenic nematodes <i>Steinernema kraussei</i> and <i>Heterorhabditis megidis</i> against the black vine weevil <i>Otiorhynchus sulcatus</i> in open field‐grown strawberry plants

Abstract

Entomopathogenic nematodes are commercially available for inundative biological control of many insects, including the black vine weevil Otiorhynchus sulcatus (F.) (Coleoptera: Curculionidae). Currently, there is a lack of commercial application tests in field‐grown crops comparing the efficacy of different species of entomopathogenic nematodes. Field trials were carried out under different growing conditions in Ireland and Norway to evaluate the efficacy of two commercially available nematode species on the market for control of the black vine weevil Heterorhabditis megidis and Steinernema kraussei. Heterorhabditis megidis was evaluated not only at temperatures ideal for this species (soil temperatures above 10 °C), but also in the low temperature trials with S. kraussei as a ‘positive control’. Steinernema kraussei is sold as a cold active product and was therefore evaluated at low soil temperatures (below 10 °C). The overall results indicated that H. megidis was effective as long as temperatures were optimum (not dropping below 10 °C). For S. kraussei , the results obtained were rather disappointing, where control barely reached 50% in the trial with the coldest temperature. Temperature and soil type appeared to be a major limiting factor for the efficacy of both nematode species. On the basis of the results and experience obtained in these trials, the future implications for biological control of O. sulcatus with entomopathogenic nematodes in commercial field‐grown strawberry production are discussed.