Purple
Loosestrife
The Beautiful
Invader
Sharon Gillies +
Alida Janmaat
Purple loosestrife is
easy to identify
when in blossom.
Lessoning Loosestrife
Winter
Fall
Spring
Summer
Hard to ID the rest of the year
• 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 Loosestrife
Where does it live?
• Moist soil to shallow water
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–
–
–
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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 Valley
Our 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 Loosestrife
What 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 Loosestrife
How 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 Stalks
Credit: MJ Kewley
Org: Great Lakes Indian Fish &
Wildlife Commission (GLIFWC)
Purple Loosestrife
How 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 Loosestrife
What 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