Pesticides and passive dispersal: acaricide‐ and starvation‐induced take‐off of the predatory mite Neoseiulus baraki

Abstract

An understanding of the causes and consequences of dispersal is vital for managing populations. Environmental contaminants, such as pesticides, provide potential environmental context‐dependent stimuli for dispersal of targeted and non‐targeted species, which may occur not only for active but also for passive dispersal, although such a possibility is frequently neglected. Here, we assessed the potential of food deprivation and acaricides to interfere with the take‐off for passive (wind) dispersal of the predatory mite Neoseiulus baraki. Wind tunnel bioassays indicated that starvation favoured the take‐off for wind dispersal by the mite predator, which also varied with wind velocity, and dispersal increased at higher velocities within the 1–7 (m s−1) range tested. For the acaricides tested, particularly the biopesticide azadirachtin but also abamectin and fenpyroximate, the rate of predator take‐off for dispersal increased, and further increased with wind velocity up to 7 m/s. Such responses were associated with changes in the predator behavioural preparation for wind‐mediated passive dispersal, with a greater incidence of the standing posture that permitted take‐off. The rate of take‐off for passive dispersal by N. baraki increased with food deprivation and exposure to the residues of agricultural acaricides. Azadirachtin exposure resulted in a particularly strong response, although abamectin and fenpyroximate also stimulated dispersal.