Trichomes and spider-mite webbing protect predatory mite eggs from intraguild predation

Predaceous arthropods are frequently more abundant on plants with leaves th at are pubescent or bear domatia than on plants with glabrous leaves. We ex plored the hypothesis that for some predatory mites this is because pubesce nce affords protection from intraguild predation. In laboratory experiments , we tested whether apple leaf pubescence protected Typhlodromus pyri eggs from predation by western flower thrips, Frankliniella occidentalis. To inv estigate the effect of pubescence further, we added cotton fibers to tricho me-free leaves. We also determined whether webbing produced by Tetranychus urticae protected Phytoseiulus persimilis eggs from predation by F. occiden talis. Predation by thrips on ir: pyri eggs oviposited on field-collected p ubescent "Erwin Bauer" apple leaves was significantly less than on glabrous "Crittenden" apple leaves. Phytoseiid eggs oviposited in the cotton fibers were preyed upon significantly less than those on the trichome-free bean d isk. Increasing the cotton fiber density from 5 to 20 fibers only slightly further reduced predation by thrips on T. pyri eggs. Thrips fed upon signif icantly fewer P. persimilis eggs oviposited in Te. urticae webbing than egg s oviposited on a surface that differed only in the absence of Te. urticae web. We conclude that a complex leaf topography reduces intensity of intrag uild predation in this system.