Why Use Galerucella Beetles to Control Loosestrife?
Galerucella calmariensis and Galerucella pusilla are humble looking leaf-feeding beetles that have grown to an importance far beyond their 6mm length, at least to invasive plant management efforts. These insects have become an integral part of the control of purple loosestrife, a plant that is capable of producing dense monocultures in wetland and riparian areas, crowding out cattails and other native species as well as significantly altering the water flow in waterways and canals. Patches of purple loosestrife can become so large, and can occur in and around such sensitive habitat, that control through chemical or mechanical methods can become prohibitively expensive and impracticable. The utilization of Galerucella as part of an integrated pest management plan can result in increased purple loosestrife control over several years, at minimal cost. Adult Galerucella beetles and larvae consume the foliage and growing shoot tips of purple loosestrife, reducing plant growth, limiting flowering ability, causing the plant to deplete its root starch reserves, and with enough beetle and larva density, killing the plant. Galerucella infestations have the ability to reduce purple loosestrife populations enough to allow native plants to re-establish, restoring ecological functions to the wetland or riparian area.
Galerucella calmariensis and G. pusilla are native to the same European and Asian range as purple loosestrife and help keep its populations from reaching the monocultures that can occur in North America. Extensive research was done over several years in Europe to determine what possible biocontrol agents existed, with the first and foremost criterion for selection being that the biocontrol agents be incapable of completing their life cycle on plants other than purple loosestrife. This would prevent damage to non-target plant species by the biocontrol agent. Galerucella calmariensis and G. pusilla, along with a root-mining and a flower-feeding weevil, fit the criteria of not completing their lifecycle on any North American plant other than purple loosestrife, and were approved for releases in the United States in the early 1990s. These biocontrol agents have since been released in at least 33 states, including West Virginia, with important and extensive monitoring programs in place to determine the effectiveness of the control and to ensure the agents are not damaging other native species as well.
Bioassessment and management of North American freshwater wetlands
By Russell Ben Rader, Darold P. Batzer, Scott A. Wissinger