Now that Galerucella calmariensis is well established in many parts of Michigan, the Purple Loosestrife Project is shifting its focus from beetle rearing and release, to field collection and redistribution efforts. Redistribution simply involves collecting Galerucella in the spring from established sites and re-releasing them in sites where they do not yet occur. Redistributing beetles soon after the begin activity in the spring is very effective as they are naturally ready to lay eggs. As little as 20-30 spring-collected beetles can effectively inoculate a new site when redistributed in the spring. Much larger numbers would be required from summer redistributions because summer-collected beetles will likely not lay eggs until the following spring.

Collection is best done on warm sunny days when Galerucella adults are actively feeding on the growing tips of purple loosestrife and can frequently be found in mating pairs. This typically occurs in mid May to mid June in southern Michigan (about 7-10 days later in northern Michigan and 10-15 days later in the Upper Peninsula). The collection equipment is very simple and consists of a funnel and multiple collection containers to hold the insects for transport. A plastic pop bottle top can be cut off, inverted, and secured with tape to make a self contained collection-storage container.

“Collectors” should come to the site with collection devices, multiple collection containers (to avoid overcrowding of beetles) and a large cooler with ice packs to keep beetles cool for transport to the release site. Hip boots or waders may be necessary for full access to sites. Collect a minimum of 20-30 beetles per site to be inoculated. If possible, inoculation with up to 200 beetles per site should be done to ensure establishment. If more than 200 beetles are available, consider distributing the rest among several sites.

Redistribution sites should be surveyed prior to release to determine if they may already have established populations of Galerucella. If so, selection of alternative sites is recommended. Once collected, beetles should be kept out of direct sunlight to avoid overheating. Storing collection containers in a cooler on ice is recommended. Releases of beetles should be done as soon after collection as possible. At the release site, avoid dumping the containers as this will result in beetles falling off the plant, rather, gently open the collection container and place in a loosestrife plant. The beetles will crawl out directly onto their host, increasing the chance they will start to feed. In this way any extraneous seeds or loosestrife foliage will remain in the container and can be removed from the site. Placing all the beetles within a few meters of each other is recommended as this will ensure they have ready access to mates etc. Beetles will naturally redistribute themselves in the wetland over the next several seasons.

Public involvement with field collection and redistribution efforts in Michigan along with the natural dispersal of Galerucella will ensure that beetle populations are soon established in most infested wetlands.

Photos courtesy: Dr. Luke Skinner, MN DNR