Interaction between the entomopathogenic nematode, Steinernema feltiae and selected chemical insecticides for management of the tomato leafminer, Tuta absoluta

Entomopathogenic nematodes are an important component of integrated pest management programs. This study aimed to determine the interaction between abamectin, azadirachtin, indoxacarb, chlorantraniliprole, dichlorvos and metaflumizone with two isolates of Steinernema feltiae (Filipjev) for the control of Tuta absoluta (Meyrick). The effect of recommended doses of the chemical insecticides on survival of S. feltiae and infectivity against Galleria mellonella (L.) larvae as a model organism were tested. Dichlorvos and abamectin were highly toxic to S. feltiae. Moreover, azadirachtin was moderately toxic to the nematodes, but significantly reduced nematode infectivity on G. mellonella. In interaction tests, S. feltiae isolates were applied at LC50 level, 0, 12, 24 and 36 h after larval of T. absoluta treatment with LC10 or LC25 of the insecticides. Out of 96 combinations the numbers of synergistic, additive and antagonistic interactions were 12, 57 and 27, respectively. Most of the antagonistic effects were observed when the nematodes were applied immediately or 12 h after the insecticide treatments.