What is purple loosestrife? You’ve probably seen it, and right now it’s in full bloom.
It’s a tall plant with spires of bright purple flowers that grows in wet areas. It’s very pretty, very invasive, and very hard to get rid of.
Native to Europe, purple loosestrife was introduced to the U.S. in the early 1800s both on purpose, as a medicinal herb, and accidentally by way of contaminated ballast water on ships. It didn’t take long before loosestrife infested the eastern seaboard, and now it’s has spread through almost all of the U.S.
Purple loosestrife is remarkably difficult to remove for a number of reasons:
- Each mature adult plant is capable of producing tens of thousands of seeds;
- Its woody roots allow it to regenerate (so even after all your hard work, it might come back) and are difficult to pull up;
- It grows in wet areas, so mowing is not always an option; and
- Burning is not effective and may even damage native plants.
So how do we control this noxious weed? Many conservation organizations now use biological control.
Six different European insect species appear to be the most effective. They have been carefully studied to make sure that they don’t become an invasive problem themselves. They are host-specific, which means that they feed and reproduce solely on loosestrife.
Two of the most successful insects are the Galerucella calmariensis and Galerucella pusilla beetles. The adults and their larvae feed on the stems and leaves, stripping the plant of its foliage and reducing its ability to flower and set seed.
After obtaining permission from the state environmental conservation department to release beetles, organizations can purchase beetles from a supplier. If there is an existing beetle population, they can bolster the wild populations by raising beetles in a rearing facility. Raising your own beetles can engage local conservation partners, volunteers and even youth groups.
Partnering with the Sudbury, Assabet, and Concord Rivers Cooperative Invasive Species Management Area, Great Meadows National Wildlife Refuge of the Eastern Massachusetts Complex ran a beetle rearing facility for the second year in a row this past spring.
“Beetle rearing facility” may sound high-tech, but we’re just creating a mock wetland environment. Plastic kiddie pools provide the water, and potted loosestrife plants provide tasty food for our beetles. We dig up loosestrife root balls in early spring and plant them in pots in the pools and let them grow until they’re tall and leafy enough to support beetles. If your facility is in a publicly accessible spot (we housed ours at Assabet River refuge’s visitor center), having signs or other outreach materials lets visitors know why you are actively growing an invasive species!
After the plants are big enough, we slip fine mesh nets over them, supported by tomato cages or bamboo poles, and we collect wild beetles from local wetlands and add them to our netted pots. The nets keep the beetles in and predators out. Birds, amphibians and other insects all find Galerucella quite tasty, and we want as many of our beetle babies to survive to adulthood as possible.
After a little over a month of careful monitoring, the new generation of adults is ready for release! We grew 50 pots of loosestrife in our 2013 facility and estimate that we reared between 25,000 and 50,000 new adults. While that sounds huge, several thousand beetles are released for each infested acre.
Are you interested in starting your own beetle rearing facility? Right now is a great time to get started! Loosestrife is in full bloom, so now you can mark ideal sites to collect rootstock for your facility.
You collect the roots in early spring, when all that’s left are the dead sticks of the previous year’s growth. Flag each plant now, and collecting the roots in the spring will be a breeze!
Want to learn more? Visit our watershed blog or contact Amber Carr at email@example.com. Also be sure to check our Neponset River Watershed Association’s Flickr for hundreds of really great photos from their beetle raising efforts and all of their wonderful volunteers! You can also check out a similar effort led by our West Virginia Field Office.