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A Possible Solution: Galerucella Beetles

In 1992, after extensive studies of the insect predators of purple loosestrife in its original habitat, the USDA approved the use of two species of Galerucella beetles as biocontrol agents. These beetles live, eat, and breed exclusively on purple loosestrife, and prefer to fly long distances or die rather than eat other plant species.

Adult beetles spend the winter underground, hibernating among the roots of a purple loosestrife plant. They emerge in June, and after eating holes in the leaves of the host plant for about a week, they mate and the females soon begin laying eggs on the stems and leaves. One beetle can lay up to 300 eggs over the course of 5 or 6 weeks before she dies.

Meanwhile, the eggs begin hatching after 2 to 3 weeks, and the larvae, which have voracious appetites, begin eating the flower buds and growing tips of the plant. This behavior, called "tip feeding," causes extensive damage, leaving the plant stunted and brown. After several weeks of eating, the larvae are ready to pupate. They crawl down the stem and bury themselves in the soil.

   
  from: Alyson Loos and David Ragsdale, "Biological Control of Purple Loosestrife: A Guide for Rearing Leaf-feeding Beetles"  

In another 2 to 3 weeks the insects emerge as adults. If the plant they are on is badly damaged, they take flight in search of other loosestrife plants on which to dine. They do not lay eggs at this time; they eat for several weeks, and return to the soil in late August to begin their long winter's sleep, completing the cycle.

   
              Eggs                          Larvae                       Adult Galerucella Beetles
   Above photos from Agriculture and Agri-Food Canada Archives, Agriculture and Agri-Food Canada
        
 Galerucella beetles were released in the late 1990's at both the Great Meadows National Wildlife Refuge in Concord, MA, and the Parker River National Wildlife Refuge in Newburyport, MA. The resulting decrease in loosestrife vigor allowed the wetland species that had originally been abundant to regain their dominance.

In 2000 the Massachusetts Office of Coastal Zone Management (MOCZM) developed a Purple Loosestrife Biocontrol Project as part of its Wetlands Restoration Program. The Project has overseen the release of beetles at 10 other sites in Massachusetts, all of which are being monitored for purple loosestrife damage.

In the 2006 photos on the right, of purple loosestrife plants at Fresh Pond Reservation, bullethole patterns indicate feeding by adult Galerucella beetles, and severe damage indicates feeding by larvae. Beetles from a biocontrol program as far as 10 miles away might have flown to Fresh Pond in search of food.      
                           © 2006 E. Wylde