Establishment and impact of Lythrum salicaria on wetlands

1. Establishment and impact of Lythrumsalicaria on wetlands

2. 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

3. 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

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

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

6. 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

7. Displacement by L. salicaria Montezuma National Wildlife Refuge, New York 18 June, 1968 16 August, 1978 Thompson et al., 1987

8. 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 Blossey et al., 2001 Oregon State University

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