MONROE - On Lake Montesian, in Monticello, a very pretty but aggressive invasive wetland plant called purple loosestrife has just had a natural enemy released into it. The enemy is an insect, Galerucella or cella for short, that has an exclusive fondness for the purple loosestrife plant.
The Wisconsin Department of Natural Resources and the University of Wisconsin-Extension have done careful research and proven that these insects are not a threat to other plants. They have been using these insects for more than 20 years in Wisconsin to reduce the purple loosestrife's impact on wetlands.
The life cycle of the beetle is that the adult emerges in the spring to feed on newly formed leaves of the purple loosestrife, and then lays eggs on the stems and leaves of the plants for about two months. These eggs hatch into larvae after about 12 days. The larvae feed on the young buds and leaves at the shoot tips and other leaves for two to six weeks (depending on the species) before entering the soil or spongy stem tissue to pupate. Pupation lasts about a week and the new adult beetles emerge in late July or August. Adults overwinter in the soil near the plant.
The Green County Land and Water Conservation Department fostered these critters for a little more than the past month. In mid-May, roots of already infested plants were dug and repotted in pots gathered from Yellowstone Lake State Park in Lafayette County. Then the emerging potted plants were transported to the department's parking lot in Monroe to be netted, set in a pool of water and left to grow. The DNR supplied more cella beetles to enhance the impact. These beetles were released into the netted plants in early June. The beetles feasted on the leaves and new shoots. One plant was turning brown from the beetle activity, so it was determined it was time to release the beetles into their new environment - the shores of Lake Montesian. The netted plants were transported to the site and put next to healthy purple loosestrife. The nets were removed and inspected for adults and any size larvae, which were then set on the healthy plants. Eight pots with beetles and larvae were placed in the southwest corner of the lake and detention pond. The pots will be removed at a later date.
The hope for this project is that we can effectively control the spread of purple loosestrife on Lake Montesian with a biological approach rather than chemical. If it seems necessary, a mechanical approach could be used in conjunction with the beetles in the future.
For more information, contact Todd Jenson, county conservationist with the Green County Land and Water Conservation Department, at 608-325-4195, ext 119.
The Wisconsin Department of Natural Resources and the University of Wisconsin-Extension have done careful research and proven that these insects are not a threat to other plants. They have been using these insects for more than 20 years in Wisconsin to reduce the purple loosestrife's impact on wetlands.
The life cycle of the beetle is that the adult emerges in the spring to feed on newly formed leaves of the purple loosestrife, and then lays eggs on the stems and leaves of the plants for about two months. These eggs hatch into larvae after about 12 days. The larvae feed on the young buds and leaves at the shoot tips and other leaves for two to six weeks (depending on the species) before entering the soil or spongy stem tissue to pupate. Pupation lasts about a week and the new adult beetles emerge in late July or August. Adults overwinter in the soil near the plant.
The Green County Land and Water Conservation Department fostered these critters for a little more than the past month. In mid-May, roots of already infested plants were dug and repotted in pots gathered from Yellowstone Lake State Park in Lafayette County. Then the emerging potted plants were transported to the department's parking lot in Monroe to be netted, set in a pool of water and left to grow. The DNR supplied more cella beetles to enhance the impact. These beetles were released into the netted plants in early June. The beetles feasted on the leaves and new shoots. One plant was turning brown from the beetle activity, so it was determined it was time to release the beetles into their new environment - the shores of Lake Montesian. The netted plants were transported to the site and put next to healthy purple loosestrife. The nets were removed and inspected for adults and any size larvae, which were then set on the healthy plants. Eight pots with beetles and larvae were placed in the southwest corner of the lake and detention pond. The pots will be removed at a later date.
The hope for this project is that we can effectively control the spread of purple loosestrife on Lake Montesian with a biological approach rather than chemical. If it seems necessary, a mechanical approach could be used in conjunction with the beetles in the future.
For more information, contact Todd Jenson, county conservationist with the Green County Land and Water Conservation Department, at 608-325-4195, ext 119.