The University Record, October 2, 2000

Researchers hope an itty-bitty beetle will help control purple loosestrife

By Joanne Nesbit
News and Information Services

The beetle that may rescue wetlands from overgrowth of purple loosestrife is barely larger than the word ‘trust’ on a dime. Photo by Martin Vloet, U-M Photo Services
They were really hungry from May to July. And that was a good thing. They are taking a pause right now, but will be ravenous when they emerge again next spring.

These creatures with such voracious appetites are the loosestrife leaf-eating beetles whose diet consists solely of and whose life cycle appears to be entirely dependent on purple loosestrife, that colorful but damaging invader in wetlands from Maine to Washington and Michigan to Alabama. And these tiny beetles may be the key to successfully controlling the Lythrum salicaria where mowing, burning, flooding and herbicides have failed and, in fact, actually promoted the growth or reproduction of purple loosestrife.

The Matthaei Botanical Gardens is part of a national research program on the biocontrol of the vibrant but damaging purple loosestrife. For the past four years, the Gardens has been raising and releasing these beetles into its wetland area. By establishing 30 permanent plots (six times more than required by the national program), staff at the Gardens is able to monitor the populations of both the beetle and the plant species occurring in the plots.

“The collected data will be used to assess the success of the biocontrol program and to determine the detailed effect of loosestrife on the wetland plant community,” says Brian Klatt, Gardens associate director. “Hopefully we will be able to determine the response of the plant community to the control of loosestrife.”

The Gardens has released more than 35,000 beetles during the past three years. And while it is still too early to assess the success of the program, Klatt feels that the program will answer important questions regarding loosestrife and the management of wetlands.

“Wetlands are one of our nation’s most valuable resources,” Klatt says. “Someday we hope that the Gardens’ willow pond and other wetlands will be much less vibrant, but far healthier and more diverse.”

Home gardeners may be aware that nurseries no longer sell purple loosestrife, but they can and do offer its acceptable non-invasive cousin Lyfimachia, which comes with a yellow or white blossom.