Purple Loosestrife Biocontrol Project

Purple Loosestrife

Aimed to limit the spread of purple loosestrife, an invasive wetland plant species, throughout the Fresh Pond Reservation by biological means.  Long-term study of the success of the biocontrol efforts - namely, the introduction of the Galerucella beetle - is conducted in partnership between the Cambridge Water Department and volunteer citizen scientists from the broader community.

Sign up for our upcoming spring monitoring session, scheduled for Saturday, July 21st from 1-3:30pm! Please contact Kirsten Lindquist at (617) 349-6489 or klindquist@cambridgema.gov to sign up for meeting point details, and so there will be enough materials for all.

This is a day of outdoor science-in-action!  Please come dressed appropriately with sturdy footwear and long pants.  A water bottle, sun protection and bug repellant are recommended.

2006: The Purple Loosestrife Biocontrol project began in 2006 as a collaboration between the Friends of Fresh Pond and Cambridge Water Department.

2007: First population of Galerucella beetle purchased, reared, and released at Little Fresh Pond.

2008-2012: Additional populations of Galerucella beetles purchased and released to supplement existing adult populations. Observed damage to existing purple loosestrife populations.

2013: Existing adult population of Galerucella beetles remain adequate for purple loosestrife biocontrol - as determined by both direct evidence of beetle activity and the continued decline in purple loosestrife dominance. No new beetle populations purchased, continued monitoring to ensure efficacy of biocontrol project.

2014: Spring monitoring session is scheduled for July 21, 1-3:30 pm, meeting at Maher Park.  Fall monitoring TBD.

Purple Loosestrife, Lythrum salicaria, is an invasive wetland plant species native to Europe and Asia. It first appeared in North America during the 19th century, brought to this continent both in the ballast of ships and as an ornamental for gardens. This highly invasive plant has been observed in every state in the continental US with the exception of Florida. Purple loosestrife was first observed at Fresh Pond Reservation in the early 2000s, and had spread to inhabit shoreline space along every water body on the Reservation, as well as in several of the wetland bioswales at the beginning of this project in 2006.

As with any invasive species, purple loosestrife poses a serious risk to the ecological balance at Fresh Pond Reservation. Purple loosestrife alters the physical properties of wetlands by shading out smaller plants that would create a wetland understory and by altering the flow of water and sediments through the wetland. These alterations can limit the ability of wetlands to convert contaminants into more benign forms and recycle nutrients back into the ecosystem, which can negatively impact water quality.  

Several control methods were tried with limited success before the Biocontrol project. Cutting the purple loosestrife causes the plant to sprout more stocks, leading to increased flowering. Pulling up the plant is very difficult, and if the entire plant is not removed, the remaining root system can still send out shoots. Herbicide is not a preferable option so close to drinking water source, especially as yearly application is necessary.

Biocontrol, in the form of the Galerucella beetle, seems to be the best choice for reclaiming wetlands on Fresh Pond Reservation. The Galerucella beetle was approved for use to control purple loosestrife populations by the USDA in 1992.

Galerucella beetles are native predators of purple loosestrife in Europe. Of the 100 insects initially investigated for use as a biocontrol agent, Galerucella calmariensis and G. pusilla are two of the 4 insect species currently used in the US to control purple loosestrife. The beetles live and breed exclusively on purple loosestrife, and during host specificity testing, starved rather than eat associated wetland vegetation. The Galerucella beetle goes great distances to find purple loosestrife because it will not mate or lay its eggs on any other species of plant. The beetle will occasionally nibble on other vegetation once purple loosestrife has been depleted, but will ultimately move on, leaving the native vegetation intact. This makes this beetle an excellent biological control species.

  • Exisiting Conditions Map of Purple Loosestrife at Fresh Pond Reservation.

    Exisiting Conditions Map of Purple Loosestrife at Fresh Pond Reservation.

  • Purple Loosestrife

    Purple Loosestrife

  • Purple loosestrife in seed.

    Purple loosestrife in seed.

  • Purple Loosestrife Biocontrol presentation, Elizabeth Wylde speaking.

    Purple Loosestrife Biocontrol presentation, Elizabeth Wylde speaking.

  • Beetle rearing in nursery at the Maynard Ecology Center.

    Beetle rearing before release at the Maynard Ecology Center.

  • Beetle cage.

    Beetle cage.

  • Vinny Falcione (CWD) installing monitoring quads before beetle release.

    Vinny Falcione (CWD) installing monitoring quads before beetle release.

  • Monitoring quad.

    Monitoring quad.

  • Hannah Wilbur (CWD) releasing the beetles.

    Hannah Wilbur (CWD) releasing the beetles.

  • Close up view of beetles prior to release.

    Close up view of beetles prior to release.

  • Beetles released in purple loosestrife.

    Beetles released in purple loosestrife.

  • Location of  beetle monitoring quads.

    Location of beetle monitoring quads.

  • Galerucella beetles on purple loosestrife.

    Galerucella beetles on purple loosestrife.

  • Galerucella Beetles on Purple Loosestrife.

    Galerucella Beetles on Purple Loosestrife.

  • Beetle monitoring.

    Beetle monitoring.

  • Hannah Wilbur (CWD) monitoring beetle damage on purple loosestrife.

    Hannah Wilbur (CWD) monitoring beetle damage on purple loosestrife.

  • More beetle damage monitoring.

    More beetle damage monitoring.

  • Volunteers monitoring damage during fall.

    Volunteers monitoring damage during fall.

  • Volunteers entering the wetland to monitor during the fall.

    Volunteers entering the wetland to monitor during the fall.

  • Beetle damage on purple loosestrife.

    Beetle damage on purple loosestrife.

Have questions or comments about the Purple Loosestrife Biocontrol Project? Email us!