Denoth, Madlen Myers, Judith H. 2004-12-02 Purple loosestrife, <i>Lythrum salicaria</i>, has invaded North American wetlands over the last 200 years. A biological control project was started in British Columbia, Canada, in 1993 with the introduction of <i>Galerucella calmariensis</i>, a leaf- feeding beetle of European origin. To evaluate the success of the biological control project in the Lower Mainland of British Columbia, we monitored the defoliation levels of <i>Lythrum</i> at 10 release sites of the control agent, identified factors associated with among-site variability in defoliation levels, and determined the effect of defoliation on the performance and abundance of <i>Lythrum</i>. In tidal areas, the beetles could not establish due to tidal disturbances. The control agent established at all non- tidal sites, but defoliation levels varied considerably. Defoliation levels were negatively associated with predation on <i>Galerucella</i> eggs, suggesting that general predators may be able to prevent or delay successful biological control of <i>Lythrum</i>. Eggs on <i>Lythrum</i> stems surrounded by water experienced lower predation rates than eggs on stems on land, indicating that standing water acts as a partial refuge against predators for <i>Galerucella</i> eggs. Flower-bud density, length of inflorescence, and plant biomass per m² were all negatively related with the intensity of beetle feeding, and stem height was marginally reduced with increased beetle grazing. Dry biomass per m² of <i>Lythrum</i> appeared to decline drastically only at sites where beetle grazing was intense. application/pdf https://folia.unifr.ch/global/documents/299920 https://folia.unifr.ch/documents/299920/files/1_denoth_vsb_orig.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1016/j.biocontrol.2004.10.006 info:eu-repo/semantics/openAccess License undefined Biological Control. - 2005, vol. 32, p. 269 purple loosestrife Lythrum salicaria Galerucella calmariensis control-agent establishment insect outbreak predation plant quality tidal disturbance cumulative feeding effects info:eu-repo/classification/udc/574 Variable success of biological control of Lythrum salicaria in British Columbia http://purl.org/coar/resource_type/c_6501