Containing Purple Loosestrife

Trustee David Black reports encouraging findings with his project of releasing Galerucell beetles along the rail trail in Groton to reduce the Purple Loosestrife growth in the area. This chart shows an impressive reduction since the start of the project.  According to David, the goal of these types of biological control is to reduce the density of the invasive plant and try to keep it and its predator in some kind of equilibrium.

David further explains: “There is evidence of native species abundance increasing, and these fluctuations at lower densities are the desired outcome. This year, I changed the sampling protocol away from the fixed plots because the density at those locations was no longer reflective of the population as a whole. We are now using a larger number of randomly spaced 0.94 square meter plots, the area defined by a hula hoop. The beetles have also spread at least as far south as Groton School and this dispersal study will be given more importance in the years to come. The final good news is that I can teach an awful lot of ecology and data analysis with this activity; the graph above was produced by two ninth graders as part of a much longer report.”
The potential downside is that Phragmites australis has moved in to the newly loosestrife-free area. The infestation is still small, but it is dense. David will take a closer look at this come winter, and may at least cutback the above ground stems to slow the rate of colonization.