Intraguild Predation Among Three Thrips Species and the Two-Spotted Spider Mite Tetranychus urticae on Vegetables

Several phytophagous thrips can act as facultative predators within arthropod food webs, and this trophic flexibility may shape pest population dynamics when thrips co-occur with spider mites or conspecific competitors on shared host plants. Here we examined intraguild predation among three economically important thrips species, Frankliniella occidentalis, Thrips palmi, and Megalurothrips usitatus, and the two-spotted spider mite Tetranychus urticae, which frequently cooccur on vegetable crops. Predation assays showed that all three thrips species consumed T. urticae, but predation varied markedly with predator species, predator stage, and prey stage. Mite eggs were the most vulnerable prey stage with F. occidentalis showing high egg predation across developmental stages, while T. palmi and M. usitatus showed lower and more variable predation. Predation on active mite stages was generally weaker. Intraguild interactions among the three thrips species were limited in active-stage assays, but larval M. usitatus significantly reduced the survival of F. occidentalis eggs. Removing host plant material increased predation on T. urticae eggs, especially for F. occidentalis and T. palmi. In 20-day mixed-rearing assays, co-rearing with thrips significantly reduced active T. urticae abundance, whereas pairwise thrips co-rearing produced no clear suppression of thrips population abundance. Species-specific qPCR confirmed prey DNA in a subset of predators after feeding assays, supporting the direct trophic interactions detected in the behavioral experiments. These findings highlight the need to treat thrips not only as herbivores but also as context-dependent omnivores when evaluating pest interactions and integrated pest management strategies.