Purple Loosestrife

The Beautiful Invader

Sharon Gillies + Alida Janmaat

Lessoning Loosestrife

Purple loosestrife is easy to identify when in blossom.

Hard to ID the rest of the year

Winter Spring

SummerFall

• Introduced as a horticulture plant, it has become a problem in many areas.

• In the summer of 2007 an extensive survey of Langley, Abbotsford and Chilliwack was conducted to GPS map the distribution and abundance of purple loosestrife (Lythrum salicaria L.)

Purple LoosestrifeWhere does it live?

• Moist soil to shallow water– Wet meadows and pastures– Marshes and wetlands– Stream and river banks– Lake shores – Roadside ditches

• Can tolerate drier conditions– Lawns and gardens– Agricultural and pasture land

http://www.dnr.state.wi.us/org/land/er/invasive/info/loose2.htm

Spreading in the Fraser ValleyOur survey found purple loosestrife

in wetlands sites which had been disturbed by human activities (dredging, etc.).

When compared with a survey completed in 1992 where 7 sites were identified in this area, we found 108 purple loosestrife sites.

We did not find any large single

species stands of purple loosestrife.

Problem areas in the Fraser Estuary – in particular in brackish areas.

Purple LoosestrifeWhat does it do?

• Invades wetlands– Out-competes and replaces native plants– Eliminates natural food and cover for wildlife– Can change the structure and function of a wetland

• Affects humans– Can clog irrigation systems

• Possible uses – Provides a nectar and pollen source for bees

www.uq.edu.au/nanoworld/ images/honeybee-1.jpg

Crowding out native species in BC?

In our study, 18 species could only be found in areas where purple loosestrife was not present.

Our data may indicate that some species are rare in disturbed wetland sites, and the presence of purple loosestrife may increase their rarity.

• The ability of purple loosestrife to crowd out native species may put some species at risk.

• We should remove it from wetland areas and prevent the spread of this invasive plant

Purple LoosestrifeHow can we control it?

• Manual (digging, pulling, cutting)– Not effective for large

infestations– Difficult and time consuming.

Must follow up annually when new plants appear.

– Remove as much of root system as possible and dispose of plants properly

Cutting StalksCredit: MJ Kewley Org: Great Lakes Indian Fish & Wildlife Commission (GLIFWC)

Purple LoosestrifeHow can we control it?

• Biological Control– Best for severe purple loosestrife infestation

(>3 acres)

– Works by using a plant’s natural enemies against it

• After years of testing to be sure the species would not negatively impact wetlands and agricultural crops, three species [imported from Germany!] were approved for use in control of purple loosestrife:

– Hylobius transversovitta tus, a root mining weevil– Galerucella calmariensis and Galerucella pusilla ,

two leaf eating beetles– Nanophyes marmoratus , a flower feeding weevil

http://www.ducks.ca/purple/faq/index.html - No.4

Purple LoosestrifeWhat can we do to help?

• Report locations where purple loosestrife is found– BC Report-A-Weed– http://www.for.gov.bc.ca/hra/Plants/raw.htm

• Request your local garden center or nursery to stop selling purple loosestrife if you find it there

• Replace purple loosestrife with native plants in ornamental gardens

Research• Alida Janmaat is conducting research on

biological control of purple loosestrife in the Fraser delta.

• Sharon Gillies, Alida Janmaat, and Steve Marsh are collaborating by measuring water quality in the Fraser River as part of the Woods Hole Oceanographic Institute’s Global Rivers Project

• http://www.whoi.edu/page.do?pid=19760