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Galerucella pusilla
Biological agent type
leaf beetle
Plant species attacked
purple loosestrife (Lythrum salicaria)
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Galerucella pusilla adult
Galerucella pusilla larvae
Images by Eric Coombs, Oregon Department of Agriculture.
host damage
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Site of attack
Buds and leaves.
Mode of attack
Young larvae feed in and on the developing buds, often destroying them, which may delay or prevent flowering. Adults and older larvae feed on leaves and cause severe defoliation.
Destructive stage
Adult and external larvae stage.
Collection and release information
Widespread in distribution.  Can be collected by sweep net June-July. Consult with ODA for availability for your area.
History in Oregon
Two leaf beetles, Galerucella pusilla and  Galerucella calmariensis were released at several locations in 1992. At the Baskett Slough National Wildlife Refuge in Polk County, spectacular control occurred in 1997 reducing plant density and flowering spikes by more than 90%. In 1999 following the crash of the beetle population plant density increased about 10%. In 2000, beetle numbers increased leading to severe damage again. Spectacular outbreaks and defoliation are becoming more common. Cooperative studies with OSU and USFWS are being done to determine the cyclic nature of the plant-insect relationship. Non target impacts on crape myrtle during outbreak numbers were shown to be minor and transitory (Schooler et al. 2003).
Beetles were found over 6 miles (10 km) from a release site near Union. Regional redistribution began in 1997. In 2005, an outbreak of beetles caused near total defoliation of purple loosestrife at the Horseshoe Lake site in Marion County, where native vegetation made a significant comeback. Since 1998, tens of thousands of adult beetles have been collected and distributed to numerous locations throughout Oregon and to other states. Off-site management is important near release sites to insure that flooding or farming does not disturb adults over wintering within 100 feet of the high water level. The beetles generally produce two generations per year.
Release status in Oregon
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