Eff ect of volatile organic compounds of entomopathogenic fungi of the genus Lecanicillium and their component, the acetic acid, on the female behaviour of the western flower thrips Frankliniella occidentalis (Pergande) (Thysanoptera, Thripidae)

Abstract

The e ect of VOCs of six entomopathogenic fungal strains from genus Lecanicillium on the behavioral responses of the western ower thrips females Frankliniella occidentalis on vegetative bean plants and in a Y-shaped olfactometer was studied. The signi cant repellent reactions of thrips females and a decrease in a number of o spring by 33-34% were revealed after treatment the beans by conidial suspensions of L. lecanii strains F2 and Vl 29 in the concentration of 1 × 107 spores/ml. Strains Vl 21 ( L. muscarium ) and Vit 71 ( L. attenuatum ), which showed a repellent tendency towards thrips females, also caused a signi cant decrease of o spring number. The strains isolated from aphids (ARSEF 2332 of L. dimorphum and Vl 13 of L. longisporum ) showed a tendency towards attractiveness. In the Y-shaped olfactometer the repellency of the F2 strain and the attractiveness of the ARSEF 2332 strain were con rmed. The in uence of the other studied strains on the thrips behavioral reactions was unreliable. Acetic acid, tested in the olfactometer at doses corresponding to its content in the fungal VOCs over growing mycelium, caused di erent reactions of thrips females depending on the acid concentration: attractive reactions at the dose of 0.17 ppm; neutral - at the dose of 0.34 ppm; and weak repellent - at 0.85 ppm. The obtained data indicate that acetic acid, contained in the fungal VOCs, e ect on the behavioral responses of thrips females. The repellant e ect of the fungal spores of the genus Lecanicillium on thrips females and the negative impact on o spring number increase the e ectiveness of entomopathogenic fungi.