|Beetles Bash Purple Plant Invaders
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|by Laura Walikainen, student writer, MTU News and Information Services|
DECEMBER 3, 2003 -- A team of Michigan Tech faculty recently defeated an unlikely invader: a pretty purple flower.
Rolf Peterson, a professor in the School of Forest Resources and Environmental Science, noticed that there was a population of purple plants taking over a pond between Houghton High School and Sharon Avenue. He identified them as purple loosestrife, a perennial wetland plant known for its heartiness and stability. The cattails native to the wetland were being out-competed and were beginning to disappear from that environment.
Purple loosestrife is an exotic species that, when introduced to a new area, can take over the natural environment. Exotic species, because they are out of their natural habitat, often have no natural competitors or predators.
"They typically don't have the predators and competitors with which they evolved, and then the plant population grows out of balance," said Leah Vucetich, a research assistant professor in the School of Forest Resources and Environmental Science who worked on the purple loosestrife problem. "Their population explodes."
At a height of three to 10 feet, each adult plant has the ability to produce three million seeds a year. This makes purple loosestrife very difficult to get rid of.
"People have tried flooding the plants, burning them and spraying them with chemicals," said Vucetich. However, these methods have been either ineffective or damaging to the environment. "People have even tried mechanical hand-pulling, but this is very labor intensive," she said. "It's also not very feasible on a large scale. It's estimated that a total of $45 million dollars is spent every year trying to unclog waterways where purple loosestrife has invaded."
So scientists in other areas stricken with purple loosestrife have tried using biological controls to combat the problem. Biological controls have created debate because they are basically introducing another exotic species into an area to deal with the original exotic species. But a specific beetle, Galerucella calmariensis, whose natural predator is the ladybug, has been found to have great success in controlling purple loosestrife invasions.
Vucetich and her husband, John Vucetich, a fellow research assistant professor in the School, heard about a scientist at Michigan State University who was raising these beetles for use as a biological control. The Vucetiches headed downstate and returned with 20 pots of purple loosestrife stumps on which 50 to 100 beetles were living. Ten pots of beetles were released at the Houghton High School pond and 10 were released along the Pike River Bridge, where there was also a purple loosestrife problem.
"We released the beetles in the summer of 1998, and by 2002 only one purple loosestrife plant could be found near the Houghton High School pond," said Leah Vucetich.
"Biological controls are fairly controversial, and the outcome is not always certain," said Leah Vucetich."But this situation was well researched before use of beetles was allowed in the United States. The beetles had a dramatic effect and worked great at the pond."