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.