Brice Prairie Conservation Association

Preserving Lake Onalaska and the Black River Bottoms

loosestrife plant

Purple Loosestrife Control Project: June 9, 2014 Update

Last Friday, the Club received 1000 Galerucella beetles from Beetles Unlimited. The beetles are used to control purple loosestrife and we have been using them in the Halfway Creek area for almost the last 15-years. Originally, we were going to purchase 2000 beetles for summer release; however, Beetles Unlimited does not offer the summer beetles anymore. So, for the price of $450 we received the 1000 beetles for spring release. While it may seem like we are getting less for more, it is actually the other way around. These 1000 beetles will reproduce yet this year and give us far more beetles for the money than if we would have purchased the 2000 summer beetles, which would not reproduce this year.

As mentioned the beetles were released last Friday near Halfway Creek. When we walked down to the release site, I was pleased to see significant damage to a number of loosestrife plants along with a number of overwintering adult beetles. While the loosestrife density in the area has increased over the last few years, beetles are still present and overwintering. We have to remember that the reoccurring loosestrife is part of a cycle. Typically beetles are introduced to an area infested with purple loosestrife. It takes a few years for the beetle population to increase and establish a foothold in the area. At this point, the beetles start to reduce the loosestrife density. As the loosestrife density decreases, the beetle population also decreases as the food source decreases. With the beetle population now in decline, the loosestrife begins to once again flourish. The beetle population then increases and starts to knock down the loosestrife. Right now, we are at a point of high loosestrife density and an increasing beetle population.

We will likely never totally eliminate loosestrife from the area as loosestrife seeds float and can remain viable for up to 10 years. We can, however, keep it in check with periodic releases of beetles. Attached are a few photos from last week showing the damage that we saw on some of the plants, along with the beetles that we released.



Healthy Galerucella spp. beetles that had overwintered at the Halfway Creek site, as found in June 2014

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Leaf damage done to purple loosestrife plants at Halfway Creek by Galerucella spp. beetles that had overwintered at the Halfway Creek site, as found in June 2014

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