Purple Loosestrife Control
Purple loosestrife is a beautiful woody perennial plant that was brought from Europe by gardeners in the 1800s. It escaped from gardens and established itself in Wisconsin wetlands in the 1930s. With no predators to keep it in check, it quickly became invasive, pushing out native plant species to become the only show in town. By eliminating native plants, it removes sources of food and shelter for wetland animals, insects and waterfowl. Some species may disappear entirely. Hunting, fishing, trapping, bird watching and boat travel become impossible. A purple loosestrife-filled wetland does not filter and store water like a wetland that consists of a variety of native plants.
Purple loosestrife grows two to seven feet tall and from July through October displays tiny. bright purple flowers closely attached to four-sided spiky stems. Some plants have up to fifty stems, making for a bushy look. Young plants produce 100,000–300,000 tiny seeds per year while older plants can produce 2.5 million. Plants often grow in intertwined clumps and the below-ground root mass of each plant can extend several feet.
After 70 years of uncontrolled invasion and many years of testing, an insect called the galerucella beetle was imported from Europe to control purple loosestrife. Wisconsin DNR began a program of raising and releasing the beetles in 1994. In the early 2000s, Butte des Morts Conservation Club members worked with students from UW-Oshkosh and the Boy Scouts to raise and release these beetles on Terrell’s Island. Almost 20 years later, the project can be considered a success!
You might ask how it can be considered a success since you will still see plenty of purple loosestrife while hiking the Terrell’s Island trails. If you look closely though, you will also see tiny 1/8-inch galerucella larvae and beetles crawling on the plants. Many of the leaves are full of holes or completely withered causing them to fail to flower or to die. The goal isn’t to entirely eradicate purple loosestrife which would be unrealistic anyway, but rather to keep it from being the only species in the marsh. And we actually don’t want it all to die out. If it did, the beetles would also die for lack of food, leaving the marsh ripe for another purple loosestrife invasion should a seed or root piece survive.