Artificial selection for aerial dispersal tendency in Phytoseiulus persimilis (Acari: Phytoseiidae)

Abstract: The two-spotted spider mite (Tetranychus urticae) is one of the most importantpests worldwide. The predatory mite Phytoseiulus persimilis is a biological control agentcommonly used to suppress spider mite infestation in crops and ornamentals in greenhousesand fields. This is a specialist predator of spider mites and therefore it goes extinct from thecrop after it eliminated its prey. Thus, growers need to do multiple releases in order to securethat the predator will be present when another spider mite outbreak appears. Creating predatorstrains with desirable traits, such as high dispersal tendency, that could remain on the croplonger can lead to a more effective biological control. Theory predicts the existence of twotypes of predator dispersal strategies: a strategy with high dispersal tendency, which is calledMilker, and a strategy with low dispersal tendency, which is called Killer. It has not beenestablished, however, whether dispersal tendency of this predator is genetically determinedand heritable. In this study, we selected for the earliest and the latest dispersers from roseleaves with two-spotted spider mites. We show that 6 rounds of strong selection for early orlate dispersal resulted in a line of P. persimilis displaying earlier or later dispersal,respectively. Moreover, in a population dynamics experiment we show that by selecting fortiming of dispersal, we also obtained lines that differ in interaction time with the prey,cumulative number of dispersers, and population growth rate. We conclude that timing ofdispersal is a heritable trait that can be selected for. This study can provide a basis forbreeding programs to create strains with desirable traits and improve biological control oftwo-spotted spider mites.