Recent research has shown that leaf trichomes can positively influence the abundance of phytoseiids in at least three ways; by affording protection from predation, by increasing capture of alternative foods, and by reducing dispersal. On apples, the phytoseiid Typhlodromus pyri is more abundant on cultivars with moderate to high numbers of trichomes compared to cultivars with few or no trichomes. However, most commercial apple cultivars have moderate to high numbers of leaf trichomes. We conducted studies to determine whether the same patterns would be manifest in grapes where there is considerable variation in leaf trichomes among commercial cultivars. Eleven grape cultivars planted in a common garden were sampled during each of three years. Densities of T. pyri were estimated and leaf trichomes were rated using several scales. The leaf trichome ratings were consistent among years. Nearly 80% of the variation in T. pyri numbers each year was explained by the density of leaf trichomes and the size and density of domatia. An experiment was conducted using potted grape plants to study the pattern among leaf trichomes, T. pyri, and the phytophagous mite Panonychus ulmi. Vines from cultivars sampled in the common garden were subjected to one of three treatments; T. pyri added alone, T. pyri and P. ulmi added, and P. ulmi added alone. Cultivars with the highest numbers of T. pyri were the same as those in the common garden study. Highest numbers of P. ulmi were recorded on the cultivar with the fewest T. pyri.
Species 1: Parasitiformes Phytoseiidae Typhlodromus pyri
Species 2: Acari Tetranychidae Panonychus ulmi (European red mite)
Keywords: leaf trichomes, tri-trophic interactions
Back to Display Presentations, Subsection Ca. Biological Control
Back to Posters
Back to The 2002 ESA Annual Meeting and Exhibition