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Collecting Purple Loosestrife Beetles in the Field

June 23, 2011

Galerucella beetles can be purchased from growers in several locations, but can also be collected from previous release sites that have an established population of beetles. We are fortunate enough to have just such a site 20 miles from our rearing location, at a wetland near Buckhannon, West Virginia. This wetland had an initial beetle release 10 years ago, orchestrated by the West Virginia Department of Agriculture (WVDA). I was fortunate enough to be invited to come along with David Dick and Laura Miller of the WVDA to collect beetles with them.

Laura Miller, WVDA Taxonomic Entomologist/Museum Curator

We brought sweep nets and small containers to hold the beetles, as well as a cooler with ice and towels for the beetles to chill out in on the way home. We also brought some sturdy boots to traverse the wetland.

David Dick, WVDA Agricultural Weed Specialist

To collect the beetles, sweep the nets in an upward motion along the loosestrife plants, or bend the plants into the net and tap them. Galerucella beetles will fall off of a plant that is disturbed, making them easy to collect. Once your net is fairly full of bugs, you can aspirate Galerucella beetles into holding containers. Make sure you only collect Galerucella beetles in your holding containers, especially avoiding collecting any spiders (who would gladly feast on the beetles!). An aspirator can be purchased or constructed prior to your day in the field. Here are some instructions on making your own:

Using a sweep net to collect beetles from the Triangle Wetland

If you are transporting the beetles a long distance and keeping them in the containers for more than a few hours, the containers should have a way to get fresh air into them, such as a mesh top. If not, an enclosed container such as a film canister or other small lidded container will work fine, as long as it has some loosestrife material in it for the beetles to munch on while they are transported. Keep your insects in the cooler on your way to your rearing site, and you can either place the containers in the sleeve cages when you arrive or tip the beetles out onto the plants, where they can begin happily feeding on their new home.

Triangle Wetland, 2001

Laura Miller spearheaded orchestrating and monitoring a Galerucella release in 2001. At that point there were practically no cattails in this wetland, which is unusual since they are such strong competitors for space. The purple loosestrife was a near monoculture that almost completely obscured the pvc poles put up to mark plots for monitoring. Now, ten years later, it is a challenge to find purple loosestrife in this wetland. It is still there, but the population is considerably smaller, nowhere near a monoculture now. Cattails, willows and other wetland plants are in abundance, and are in fact growing alongside purple loosestrife.

Triangle Wetland, 2010

Laura mentioned how hard it was to walk through the woody loosestrife stems to collect beetles in previous years, and was amazed at how easy it was to navigate the wetland now that the beetles had really gotten a handle on the purple loosestrife population. This is a textbook example of a biocontrol agent doing exactly what is expected. Biocontrols will get a population down to a manageable size, but will almost never eradicate it. The population can then either be left alone and efforts focused on more pressing infestations, or be taken care of much more efficiently and effectively with a much smaller effort. As long as a biocontrol agent is thoroughly and properly studied before a release to ensure no side-effects, biological control can be an excellent tool for invasive species management.

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