Illinois Natural History Survey - University of Illinois

Signs of Impact in Illinois

Survival of released beetles

Recovery of beetles the spring after release the previous summer has been pretty much universal throughout all sites in Illinois. Some sites have been slower than others to demonstrate growth in the beetle populations but this is to be expected as all sites are different. One of the sites that shows significant development of beetle populations and impact on purple loosestrife is shown below.

Savanna in Carroll Co.

In 1997 Ed Anderson, the person handling release and observations at this site, called to say that he did not think he needed any more beetles for release there. This was most interesting and the photos below show that he was right. The original release was made in 1994 dividing 1,000 beetles between three locations within the site. Subsequent releases were made in 1996.

This is at release site 2 as it appeared in August 1997. A relatively small area of defoliated loosestrife, surrounded by an area where the loosetrife is not flowering then, in the background some flowering is seen.







The photo to the right is taken in August 1998 at site 3. Defoliated loosestrife can be seen near the distant point, far beyond the area defoliated in 1997.




In the aerial photo above it is possible to see the defoliated areas (brown) of purple loosestrife at Savanna as of August 1998. The two blue circles indicate release areas 2 and 3 from right to left. The size of the circles approximates the area of defoliation seen in August 1997. The extent of 1998 defoliation is considerably larger than that seen in 1997. The purple arrow shows defoliation about 200 m away from the original release site. Some flowering can still be seen near the trees to the right of release site 2. In the spring of 1999 we documented beetles defoliating loosestrife one mile to the east of these release points. That would be to the left in this photograph.

Information on this page maintained by David Voegtlin.

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