PEST STATUS OF WEED

Purple loosestrife, Lythrum salicaria L., (Fig. 1) is a weed of natural areas and its spread across North America has degraded many prime wetlands result-ing in large, monotypic stands that lack native plant species (Thompson et al., 1987; Malecki et al., 1993). Established L. salicaria populations persist for de-cades, are difficult to control using conventional tech-niques (chemical, physical, and mechanical), and con-tinue to spread into adjacent areas (Thompson et al., 1987). Purple loosestrife has been declared a noxious weed in at least 19 states. Nature of Damage Economic damage. With the exception of reduced palatability of hay containing purple loosestrife and reduction of water flow in irrigation systems in the West, purple loosestrife does not cause direct eco-nomic losses. Indirect losses accrue due to reductions in waterfowl viewing and hunting opportunities. Ecological damage. The invasion of L. salicaria alters biogeochemical and hydrological processes in wetlands. Areas dominated by purple loosestrife (Fig. 2) show significantly lower porewater pools of phos-phate in the summer compared to areas dominated by Typha latifolia L. (Templer et al., 1998). Purple loosestrife leaves decompose quickly in the fall re-sulting in a nutrient flush, whereas leaves of native species decompose in the spring (Barlocher and Biddiscombe, 1996; Emery and Perry, 1996; Grout et al., 1997). This change in timing of nutrient release at a time of little primary production results in sig-nificant alterations of wetland function and could jeopardize detritivore consumer communities adapted to decomposition of plant tissues in spring (Grout et al., 1997). Figure 2. Wetland dominated by purple loosestrife. (Photo by B. Blossey.) Specialized marsh birds such as the Virginia rail (Rallus limicola Vieillot), sora (Porzana carolina L.), least bittern (Ixobrychus exilis Gmelin), and Ameri-can bittern (Botaurus lentiginosus Rackett), many o