Galerucella pusilla and Galerucella calmariensis
Beetle, leaf feeding beetle (1,2)
Biological Weed Control Links Photos: G. pusilla larva Galerucella sp. larva & adult
Common Name: leaf feeding beetles, defoliators of purple loosestrife. (1,2)
Origin: These species originated in Europe and Asia where their host plant, purple loosestrife, also originated. (1,2)Life Cycle:
Egg Stage: The whole stage from egg to adult takes about 6 weeks. Approximately 2 to 10 eggs are laid in groups on leaves and stems. The egg laying process takes two months during the spring months and there can be as many as 400 eggs laid by one female in a year. The eggs hatch about one week after the female lays them. (1,2)
Larvae Stage: After hatching, the young larvae feed on developing leaf buds. As they get older, larvae feed on all above ground plant parts, such as the leaves and the stem. When they are done devoloping, they pupate in the soil or leaf litter. The larvae look like tiny caterpillars with black heads and yellowish bodies. (1,2)
Pupil Stage: The pupation stage of their life cycle goes on in the soil or in leaf litter near the plants. The beetles usually emerge out of the winter pupation stage during the months May, June, and July. (1,2)
Adult Stage: The adults, 4-6 mm in size, emerge in the spring months. The adults feed on new leaves and shoot tips and live around 8-10 weeks. Adults are very mobile and can very easily find new purple loosestrife plants to live on. After laying their eggs, they usually are dead by June. The only real difference between G. calmariensis and G. pusilla is what they look like.
G. calmariensis: Is light brown, and has a black triangle on the thorax which is mainly the only difference between the two. The body has correspondent sides, and is covered with dots and dense hairs.
G. pusilla: Is also light brown, and has a dark stripe on the thorax. The body has correspondent sides fine, dense hairs, and a little narrowing at the head. (1,2)
Type of Damage: Larvae cause stripping of photosynthetic tissue off individual plants in high amounts. The larvae eat the developing leaf buds and stems, and usually like to do so on the under side of the plants. The adults also like to feed on the under side and you can usually find holes in the leaves and stems from them. The adults like to feed on the smaller plants and shoots, unlike the larvae. (1,2)
Host Impact: The entire purple loosestrife population can loose foliage causing increased plant destruction. Less severe attacks have reduced shoot growth, seed production, and root growth. The attacked plants are smaller and appear bushier than unattacked ones. (1,2)
Release Habitat: Purple loosestrife is a weed that lives in wetlands and has infested much of North America. Currently, purple loosestrife lives in Southeastern Canada, the Midwestern U.S., the Northeastern U.S., and in small spots in the Western U.S. and Southwestern Canada. The plants spread because irrigation systems provide something for it to travel through. G. pusilla and G. calmariensis donít thrive well in shade or in areas with a lot of deep water. (1,2)
Collection, Transportation, and Redistribution: The best time to find the adult beetles is in late May to early June and the beetles can usually be found on the underside of the plants. Collection can be done by putting a bag over the plant using the bag to gather the beetles. After collection, the adults can be shipped from June until the end of July and should be transported in some sort of bag. To prevent the adults from immediately leaving the area, the bags should be left over the plants for 2-3 days. (1,2)
Purchase: They are not available commercially at this time. (1)
Remarks: These leaf-feeding beetles were introduced to North America in 1992-93. Original release sites were New York, Maryland, Oregon, Virginia, Minnesota, Pennsylvania, and Washington in the U.S., and sites in Canada. New releases since then have been made in Indiana, Iowa, Ohio, Illinois, Colorado, Michigan, South Dakota, Wisconsin, and Montana. Almost everything of the two species are pretty much the same except for the appearance. It is predicted that the beetle will reduce the purple loosestrife by 90%. (1,2)
1. Weeden, Shelton, and Hoffman. Galerucella calmariensis and G. pusilla. [Online] Available
http://www.nysaes.cornell.edu/ent/biocontrol/weedfeeders/galerucella.html, Feb.21, 2000
2. Unknown author. Galerucella calmariensis/ pusilla. [Online] Available
http://www.dnr.cornell.edu/bcontrol/galeruce.htm, Feb.21, 2000.
By: Neal Bell 3/20/2000
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