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Nature Conservancy Enlists Bug’s Aid at Houghton Lake
Conservation Groups Fighting Invasive Purple Loosestrife with Imported Beetle
CULVER, IN — Purple Loosestrife is a non-native plant and one of the worst wetland invaders in the Great Lakes region, causing untold millions of dollars of damage each year. Efforts to fight it and stem its invasion are costly, time-intensive and often unsuccessful. The Nature Conservancy has thus turned to a European beetle to help battle purple loosestrife at Houghton Lake in Marshall County.
“Purple Loosestrife is capable of quickly colonizing and dominating wetlands, displacing native plants and the animals that depend on them,” said Stuart Orr, field steward for the Conservancy. As such, many Indiana wetlands have become biological deserts because of this non-native, invasive plant. Orr says, “The Nature Conservancy will not allow this to happen at Houghton Lake.”
Houghton Lake is a wonderful example of a highly alkaline natural lake. It lies at the bottom of a broad valley that likely once carried off massive quantities of glacial meltwater. The lake is primarily fed by groundwater discharges from the surrounding hills of rolling glacial till. The Nature Conservancy purchased Houghton Lake in 2006.
According to Orr, the Conservancy normally uses herbicides to control Purple Loosestrife. This is most effective on small populations and new infestations. The main population of purple loosestrife at Houghton Lake, however, consists of about 25 dense acres that are particularly difficult to access. Here’s where the bugs come into play.
Two beetles, Galerucella calmariensis and G. pusilla, have been used since the early 1990s in Indiana as biological control agents for Purple Loosestrife. In Indiana and numerous sites throughout the Great Lakes, Purple Loosestrife biocontrol programs have been reported to have significantly reduced dense infestations, generally within five years of the initial release. These beetles were thoroughly vetted in an extensive testing program to make sure they would not become pests of any other plant. Therefore, when the Purple Loosestrife populations decline, the beetles will also, keeping things in balance.
Both beetles were released approximately ten years ago by the Department of Natural Resources about four miles to the southeast of Houghton Lake at another wetland site. Rich Dunbar, regional ecologist for the DNR’s Division of Nature Preserves, was instrumental in that beetle release. Says Dunbar, “Since Galerucella beetle introductions started in 1994, we have seen significant reductions in purple loosestrife at many of the release sites, resulting in healthier, more diverse wetlands.”
Most of the land in between this site and Houghton Lake Nature Preserve is currently developed or in agriculture, limiting dispersal opportunities for the insects. Therefore, this spring Conservancy and DNR staff will collect beetles from one or more established populations and release them at Houghton Lake and one other Conservancy preserve.
The Nature Conservancy is a leading conservation organization working around the world to protect ecologically important lands and waters for nature and people. The Conservancy and its more than 1 million members have protected nearly 120 million acres worldwide. Visit The Nature Conservancy on the Web at www.nature.org.
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