Although only time will tell whether Tetrastichus setifer will control the lily leaf beetle as effectively in Ottawa as it does at the initial release sites in New England, biological control can boast some remarkable success stories here in Ontario. Arguably the most dramatic of these is the control of purple loosestrife by the beetle Galerucella calmariensis. G. calmariensis was one of two leaf beetles released throughout Canada in the 1990’s. It is now the dominant herbivore of purple loosestrife throughout Ontario, and its impact is visually striking.
The photo below was taken along Greenbelt trail 10 near Shirley’s Bay in 2004, just west of Ottawa, where the beetle had caused substantial damage to the plants. Plants at that site produced only a few stunted flowering shoots.
The photo below was taken along Greenbelt trail 10 near Shirley’s Bay in 2004, just west of Ottawa, where the beetle had caused substantial damage to the plants. Plants at that site produced only a few stunted flowering shoots.
Compare the damaged plant above to a typical undamaged stand (below). The photo of the undamaged stand was taken at Petrie Islands to the east of Ottawa in 2004. A few beetles were spotted there that summer, but their population had not yet reached the level at which feeding damage was evident.
While this would appear to be good evidence of the impact of the beetle on the plant, we don't actually know what the plants at the Shirley's Bay site looked like before the beetles did their damage. Perhaps the Shirley's Bay area was never a good site for loosestrife and the plants were stunted even before the beetle arrived. In fact, an article last fall in the Ottawa Citizen suggested that purple loosestrife is not well adapted to many wetland types and fails to thrive, and that this, more than the release of the beetle, explains the "fading away" of the "purple menace".
The best evidence for the impact of a biological control agent involves taking measurements of the target before and after the agent has been released. Unfortunately, funding for well designed before-and-after studies is often unavailable. An alternative approach involves comparing the target at sites with and without the agent, as long as those sites are matched for as many other factors as possible. To learn more about one such study, and to help track the distribution of the loosestrife beetle, visit
purpleloosestrifebeetletracker.weebly.com.
The best evidence for the impact of a biological control agent involves taking measurements of the target before and after the agent has been released. Unfortunately, funding for well designed before-and-after studies is often unavailable. An alternative approach involves comparing the target at sites with and without the agent, as long as those sites are matched for as many other factors as possible. To learn more about one such study, and to help track the distribution of the loosestrife beetle, visit
purpleloosestrifebeetletracker.weebly.com.