Spider mites avoid plants with predators

While searching for food, prey can use cues associated with their predators to select patches with a reduced predation risk. In many cases, odours ind icate the presence of both food and predators. Spider mites are known to us e odours to locate food and mates, but also to avoid interspecific competit ors. We studied the response of the two-spotted spider mite, Tetranychus ur ticae, to cues associated with the presence of their predators, the phytose iid Phytoseiulus persimilis. We found that the spider mites strongly avoid plants defended by this predator, but do not avoid plants with another pred atory mite, Neoseiulus californicus. Since P. persimilis is commonly used i n the greenhouse where our strain of T. urticae was collected and strains o f this pest are known to adapt to greenhouse environments, we hypothesize t hat there has been selection on the pest to recognize its enemy. We further hypothesize that there has been no selection to recognize N. californicus, as it has not been used against two-spotted spider mites in the greenhouse where our spider mites were collected. We discuss the implications of avoi dance of predation by spider mites and non-lethal effects of predators for biological control of this pest in greenhouses.