Trichomes are considered the first line of defense against herbivorous arthropods, but they can also hinder the activity of predatory mites. Here, we examine the impact of tomato trichomes on development, survival and movement of the two spotted spider mite (TSSM), Tetranychus urticae, and this predatory mite, Typhlodromus (Anthoseius) recki. Eight genotypes of tomatoes (Solanum lycopersicon) and wild relatives (Solanum spp.) with contrasting densities and types of trichomes were chosen and trichomes on leaves, petioles and stems characterized. Plants were infested with TSSM females and three weeks after dead mites on glandular trichomes and alive mites were counted. On leaves where mites were introduced, TSSM numbers were not affected by tomato variety while it did in the rest of the plant. Negative correlations were observed between the density of glandular type-IV trichomes on petiole or stem and the number of alive mites found on the rest of the plant, suggesting that these structures affect mite dispersal. Furthermore, the number of mites stuck on glandular trichomes was highly affected by the tomato variety with higher numbers of mites trapped on varieties with the highest density of type-IV glandular trichomes on petiole and stem. These observations confirm that those trichomes act as a dispersal barrier for TSSM. When we conducted similar trials to evaluate T.(A.) recki movements and development on tomato plants infested with TSSM, we found that this predator was highly capable to cope with trichomes. Overall, results stress the potential of T. (A.) recki as a promising biological control agent.
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