Patterns in Resource Partitioning by Insect Biological Control Agents of Yellow Starthistle (Centaurea SolstitialisL.) in Washington

Abstract

Abstract Entire yellow starthistle, Centaurea solstitialis L. (Asteraceae), plants were harvested from three southeastern Washington sites in September 2004 for seed head dissections to assess intra-plant patterns in the spatial distribution of the introduced false peacock fly, Chaetorellia succinea (Costa), and peacock fly, Chaetorellia australis Hering (Diptera: Tephritidae). Thirty plants were partitioned into three height classes and collected at each site, spanning the longitudinal range of yellow starthistle in Washington. Seed head canopies were stratified into three vertical sections and individual heads were dissected to determine bioagent occupation. Logistic regression analysis using a binary logit model was performed on data collected from each of the three sites separately due to varying site effects. Explanatory variables included plant height, plant width, plant canopy stratum (apical, mid, basal), and presence of other bioagents within a head. ‘Other bioagents’ detected include the yellow ...