Establishment and impact of Lythrum salicaria on wetlands.

Establishment and impact of Establishment and impact of LythrumLythrum salicaria salicaria on wetlandson wetlandsEstablishment and impact of Establishment and impact of

LythrumLythrum salicaria salicaria on wetlandson wetlands

L. salicariaL. salicaria, an invasive weed, an invasive weed

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• 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 hypothesisPrevailing 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 Distribution of L. salicariaL. salicaria

Distribution as of 1985 Distribution as of 2001

Thompson et al., 1987 National Agricultural Pest Information System

Structure, growth forms, and field Structure, growth forms, and field identification characters of L. salicariaidentification characters of L. salicaria

Thompson et al., 1987Robert H. Mohlenbrock

Debates and argumentsDebates 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. salicariaDisplacement by L. salicaria

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18 June, 1968 16 August, 1978

Montezuma National Wildlife Refuge, New York

Thompson et al., 1987

Biological Control of L. salicariaBiological Control of L. salicaria

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• 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 marmoratusOregon State University Blossey et al., 2001

Effects of biological controlEffects of biological control

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Winchester Wasteway, Central Washington

August 1995 August 1998

Bureau of Reclamation