Establishment and impact of Lythrum salicaria on wetlands

L. salicaria, an invasive weed Common name, Purple loosestrife Considered one of the worst invasive, non- native species Forms dense homogenous stands Highly reproductive Competes vigorously with native plant species Morrison, 2002 Thompson et al., 1987

Prevailing hypothesis L. salicaria out- competes native vegetation Forms dense monospecific stands that restrict native wetland plants High competitive ability Reduces habitat for flora and fauna Thompson et al., 1987 Dech and Nonsko, 2001

Distribution of L. salicaria Distribution as of 1985Distribution as of 2001 Thompson et al., 1987National Agricultural Pest Information System

Structure, growth forms, and field identification characters of L. salicaria Thompson et al., 1987 Robert H. Mohlenbrock

Debates and arguments No experimental documentation of reduced or displaced native plants No quantitative measurements of monospecific stands May undergo large population fluctuations Evidence of fauna utilization David Brenner, Michigan Sea Grant Hager and McCoy, 1998 Keller, 2000 Treburg and Husband, 1999

Displacement by L. salicaria 18 June, August, 1978 Montezuma National Wildlife Refuge, New York Thompson et al., 1987

Biological Control of L. salicaria Much debate still occurs Four species were selected Two native European beetles, a root-boring weevil, and a flower feeding weevil that all feed on L. salicaria Studies have shown success with Galerucella species Galerucella spp. Hilobuis transversovittiatus Nanophyes marmoratus Oregon State University Blossey et al., 2001

Effects of biological control Winchester Wasteway, Central Washington August 1995August 1998 Bureau of Reclamation