Interactions between two-spotted spider mite, Tetranychus urticae and greenhouse whitefly, Trialeurodes vaporariorum on strawberry

The interspecific competition is a widespread phenomenon among the herbivores and is an important factor in shaping the herbivore communities. Plants usually mediate competition among herbivores via induced resistance, which can affect pest density, either by altering the performance or host preference of herbivores. The strawberry plants host the two-spotted spider mites (TSSM), Tetranychus urticae Koch and greenhouse whitefly (GHWF), Trialeurodes vaporariorum (Westwood) in greenhouses. We clearly observed the adverse effect of TSSM or GHWF prevalence on colonization and outbreak of the other one, therefore the possibility exists that feeding-induced changes in plant and interspecific competition are the effective factors in shaping their densities. In this study, laboratory experiments were carried out to determine whether previous feeding by TSSM on strawberry (Camarosa variety) affects the performance and oviposition preference of GHWF (as a competitor), and vice versa. Lower egg number, and the slower development as well as delayed oviposition were observed when the pests fed on infested leaves than control leaves. Furthermore, when the pests were given the choice between the non-infested and infested leaves, both pests significantly preferred the non-infested leaves. Our study concluded that feeding-induced changes in quality of host plant adversely affected the performance and oviposition preference of both pests. We suggested that these results can help to explain the different population densities of pests in presence and absence of other species and can attract the attention of farmers to the effects of interspecific competition on the densities of pests.