Foliar applied entomopathogenic nematodes Steinernema feltiae are not suitable for controlling Thrips tabaci in leek

Two field trials in leek were set up to determine and, if possible, improve the effect of spray applications of Steinernema feltiae (Filipjev) Wouts, Mracek, Gerdin et Bedding against Thrips tabaci Lindeman. The first trial focused on selecting a suitable application technique and on testing the effect of an attractant on thrips control in leek. The second trial focused on incorporating entomopathogenic nematodes (EPN) in a conventional insecticide scheme, and on the effect of mixing a surfactant in the spray suspension. S. feltiae proved to be ineffective against the foliar inhabiting life stages of T. tabaci, despite adding a surfactant and/or an attractant to the spray suspension and despite adapting the equipment. Compared with a traditional spray boom, a row application technique ensured a more even EPN deposition on the upper side and underside of both old and new leek leaves. This technique may improve the applications of fungicides and contact insecticides in leek.