A New Tool in the Toolbox for our Invasive Plant Control Program

On Monday, August 8, we released 1,745 beetles across the street from The George Washington House to control Purple loosestrife (Lythrum salicaria). The beetles were kindly provided by Robert Trumbule an Entomologist from the Maryland Department of Agriculture. A couple of years ago Robert also gave us a batch of 500 weevils (Rhinoncomimus latipes) to control Mile-a-minute (Persicaria perfoliata) another highly invasive plant in the entire Mid-Atlantic region.


Robert Trumbule (MDA), AWS staff, and Mallory Shramek (AWS' Summer Stewardship Intern) releasing the beetles.

Purple loosestrife is an invasive plant native to Eurasia, it was introduced to North America in the XIX century for its medicinal and ornamental uses. This herbaceous plant is a highly adaptable wetland invader that occurs in both tidal and non-tidal wetlands. This year we have noticed an important increase in its populations in the tidal Anacostia area and the drainage ditches along the levees. At the site where we released the beetles, the Old Port of Bladensburg Park, at a drainage ditch we have previously propagated Wild rice. That Wild rice has been an important seed source for our wetland planting operations, not to mention its plentiful benefits to wildlife. That’s why we decided to do something about it! Robert has been releasing two species of chrysomelid beetles throughout the state to control Purple loosestrife, Galerucella calmariensis and G. pusilla, they are native to Europe and were introduced to North America in 1992 solely to control the invasive weed.


The beetles are usually transported from the lab inside plastic Petri dishes within a thermal container to keep them cool, inactive and relaxed.


Galerucella beetles are about the size of a sushi rice grain. This one was warming up after being taken out from the thermal container and before release.

For those of you out there that are terrified about introducing biocontrol agents, calm down we are not introducing another invasive species! These beetles have been here in the U.S., from coast to coast for 19 years and are considered to be 100% host-specific to Purple loosestrife, meaning that they don’t pose a threat to any native plant species. Before their introduction to the U.S., the susceptibility of about 50 native plants to these beetles was tested, including species belonging to the same plant family of purple loosestrife (loosestrife family, Lythraceae). Only one North American native, the Winged loosestrife (Lythrum alatum) was a possible host. However it was determined that if given the choice the beetles avoided the Winged loosestrife. Adult beetles of both species feed on young leaves and shoots of Purple loosestrife whereas the larvae feed on bud, leaf and stem tissue.


A happy beetle in its new home!

More information about the life cycle of the beetles here. At AWS we are always trying to use new tools to fight back the abundant invasive plants in the watershed. Not only that but we have also been trying to become more systematic when it comes to prioritizing our invasive plant work according to the sites, affected habitats, the target species (and their abundance) among other considerations. This fight cannot be won by just handpulling or herbiciding plants, we have got to use other control methods at our disposal and more effectively restore native plant communities.   


Carefully tested biocontrol agents like these Galerocella beetles are an excellent tool for invasive plant control, it is a rather chemical-free and soil disturbance-free control method.

 

 

Comments

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RE: How often and how many times

Hi Steve, I'm Jorge Bogantes AWS Conservation Biologist. That's the only time we are going to be releasing the beetles at that site. Now they are in overwinter mode but we expect that they will be reproducing and spreading in the vicinity next year. If the weather conditions are favorable and the purple loosestrife is abundant they should be able to increase their populations quickly. Thanks, Jorge

How often and how many times

How often and how many times will you be releasing these? Will the build up their own populations quickly?

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