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

Abstract

Predaceous arthropods are frequently more abundant on plants with leaves that are pubescent or bear domatia than on plants with glabrous leaves. We explored the hypothesis that for some predatory mites this is because pubescence 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 investigate the effect of pubescence further, we added cotton fibers to trichome-free leaves. We also determined whether webbing produced by Tetranychus urticae protected Phytoseiulus persimilis eggs from predation by F. occidentalis. Predation by thrips on T. pyri eggs oviposited on field-collected pubescent "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 disk. Increasing the cotton fiber density from 5 to 20 fibers only slightly further reduced predation by thrips on T. pyri eggs. Thrips fed upon significantly fewer P. persimilis eggs oviposited in Te. urticae webbing than eggs oviposited on a surface that differed only in the absence of Te. urticae web. We conclude that a complex leaf topography reduces intensity of intraguild predation in this system.

Domatia reduce larval cannibalism in predatory mites

“…If this also holds for domatia, this suggests that even slight increases in spatial structure, such as domatia, may have large effects on predatory interactions. Similar findings with respect to leaf hairs were reported by Roda et al (2000) .…”

The presence of webbing affects the oviposition rate of two-spotted spider mites, Tetranychus urticae (Acari: Tetranychidae)

“…Roda et al 2000;Magalhães et al 2007). These species do not produce the web that they use, hence they will not be affected by the benefit of not producing web.…”

Influence of leaf trichomes on predatory mite (Typhlodromus pyri) abundance in grape varieties

“…Although initially controversial, evidence has accumulated in support of this hypothesis (Agrawal and Karban 1997;Norton et al 2000;English-Loeb et al 2005;Monks et al 2007). Trichomes may help moderate the eVects of low humidity (Grostal andO'Dowd 1994, but see Norton et al 2001), protect mites from predators (Roda et al 2000;Norton et al 2001;Faraji et al 2002;Seelmann et al 2007), and increase the capture of alternate food sources such as pollen and fungal spores that promote retention of generalist mite populations (Putman and Herne 1964;Kreiter et al 2002;Roda et al 2003). In a recent review, Romero and Benson (2005) suggest current evidence best supports protection from predators.…”