Date of Award
Master of Science
Since 1994, over 600,000 insect natural enemies have been mass reared and released for the biological control of purple loosestrife, Lythrum salicaria L., in Iowa. These natural enemies include two leaf-feeding beetles, Galerucella calmariensis and G. pusilla, a rootmining weevil, Hylobius transversovittatus, a flower-feeding weevil, Nanophyes marmoratus, and an aphid species, Myzus lythri. Field observations have shown that these natural enemies reduce the growth and reproduction of purple loosestrife plants. In addition to field releases of natural enemies, research was conducted in 1996 and 1997 to examine the effects of three G. calmariensis larval densities on purple loosestrife growth.;Galerucella larvae defoliated purple loosestrife plants, decreased the stem growth, and reduced the production of terminal buds that would eventually produce inflorescences. Feeding damage to plants increased significantly at higher larval densities. Survival of larvae did not differ among the three densities in either year. No differences were observed for adult body size, i.e., measurements taken on adults that emerged in each larval treatment, suggesting that intraspecific competition between larvae was minimal and density independent. Overall, G. calmariensis larvae negatively affected the growth of purple loosestrife plants demonstrating the importance of this natural enemy as a biological control agent.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Anthony B. Cortilet
Cortilet, Anthony B., "Evaluation of natural enemies released for the biological control of purple loosestrife in Iowa" (1998). Retrospective Theses and Dissertations. 16897.