Submitted to: Journal of British Columbia Entomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 11, 2011
Publication Date: December 30, 2011
Citation: Miliczky, E., Horton, D.R. 2011. Occurrence of the western flower thrips, Franklliniella occidentalis, and potential predators on host plants in near-orchard habitats of Washington and Oregon (Thysanoptera: Thripidae). Journal of British Columbia Entomological Society. 108:11-28. Interpretive Summary: Western flower thrips is an important pest of orchards that occurs also on a large number of herbaceous plant species. Its seasonal distribution on these plant species is poorly understood. Scientists with USDA-ARS, Yakima Agricultural Research Laboratory, Wapato, WA monitored over 100 species of native and introduced plants common in habitats adjacent to pear and apple orchards of the Pacific Northwest, and documented densities of flower thrips and important predators as a function of plant growth stage. The scientists found that flower thrips and its predators tend to colonize plants only as the plants come into flower, departing as bloom ends. These results help scientists and growers better predict seasonal use of habitats adjacent to orchards by this important, mobile pest.
Technical Abstract: One hundred thirty species of native and introduced plants growing in uncultivated land adjacent to apple and pear orchards of central Washington and northern Oregon were sampled for the presence of the western flower thrips (WFT) Frankliniella occidentalis (Pergande), 1895 and potential thrips predators. Plants were sampled primarily while they were in flower. Flowering hosts for WFT were available from late March to late October. Adult WFT occurred on 119 plant species and presumed WFT larvae were present on 108 of 119 species. Maximum observed WFT density on the most preferred plant species exceeded 100 individuals (adults and larvae) per gram dry weight of plant material. The most abundant predator was Orius tristicolor (White), 1879 (Heteroptera: Anthocoridae), collected on 64 plant species, all of which were hosts for WFT. The second most abundant predators were spiders (Araneae). Small spider immatures (first and second instars) of several species were common on certain host plants, and are likely to feed on WFT.