Vancouver’s magnificent Jericho Park has a welcome new attraction, one that
can’t be seen.
Several years ago, purple loosestrife, an introduced plant, was displacing
native plants. This summer it has been demolished by European beetles released
into the park’s west pond by UBC scientists.
“The beetles have reached high densities and are having a major impact on
the loosestrife plants, most of which have been killed in the pond,” says Plant
Science and Zoology Prof. Judy Myers.
“Look, it’s toast,” says Zoology graduate student Madlen Denoth, pointing
to dead brown stalks of plants that once choked the area. She and assistant
Janis Newhouse have been tracking the impact of the beetles under Myer’s supervision.
Ponds at Jericho Park are good examples of wetlands across northern North
America which have been invaded by European purple loosestrife, Lythrum salicaria.
An attractive plant, with pretty purple flowers, it is capable of taking over
wetland sites and was clearly doing just that in the early ’90s at Jericho.
In 1993, Myers released 30 individuals of a European beetle that feeds exclusively
on purple loosestrife. They had been reared at the Agriculture and Agrifood
Canada Laboratory in Lethbridge, Alta.
In 1996, beetles of the same species collected from a site in Ontario — where
they had been effective at reducing loosestrife densities — were added.
For those familiar with Jericho Park, loosestrife plants killed by beetles
are a pleasant sight. In an adjacent pond with lower densities, loosestrife
has been aggressively pulled by interested citizens.
Beetles have now been released at a number of sites around the Lower Mainland,
but they have shown the greatest impact at Jericho and several locations near
Chilliwack. The research project is looking at why the beetles are more effective
at some sites than others.
“The beetles are good dispersers, so we hope they will find new sites in the
Jericho area,” says Myers. “This summer we moved about 500 beetles from this
site to a new location in Langley where we hope they will establish and continue
to battle this invasive weed.”
In addition to the work on biological control, the study is looking at interactions
between purple loosestrife and two rare marshland plants to measure the potential
impact.
The research has been funded by the B.C. Habitat Conservation Fund and the
World Wildlife Fund.
