Agent: Flea beetle Plant species attacked: Tansy ragwort Longitarsus jacobaeae Senecio jacobaea
Impact on target plant: The adults feed on the foliage and cause significant mortality of rosettes during the winter months. The larvae feed in the roots and the leaf petioles.
Collection and release: Use a motorized vacuum unit to suck adults from rosettes in the fall. Releases of 100-500 are recommended. Because the beetle is so widespread, redistribution in western Oregon is unnecessary.
Distribution: The beetle has been released in 24 Oregon counties and is established in 21.
History: The ragwort flea beetle Longitarsus jacobaeae, introduced in 1971, the workhorse of the ragwort program, has reduced ragwort density by 95% in western Oregon. The combination of the cinnabar moth and flea beetle has nearly eliminated large outbreaks of flowering ragwort in many areas in western Oregon. Occasional flare-ups of ragwort reoccur, but the insects usually control the plants within a couple of years. Plant competition is an important factor in maintaining biocontrol of ragwort. In 2007, cooperative research project with Dr. Mark Schwarzländer and staff (U of ID), looked into the feasibility of using the Swiss biotype of the flea beetle to control infestations in Eastern Oregon, where the Italian biotype is ineffective. Releases of the Swiss biotype were made in Umatilla County in 2007 and in Umatilla and Union Counties in 2008. The insect readily established in similar habitats in Idaho and Montana. Monitoring in 2010 and 2011 for the Swiss biotype did not show that that the beetles established in eastern Oregon. Flea beetle populations can exist where host densities are low.
Oregon Department of Agriculture Noxious Weed Control Program Photos by Eric Coombs, Oregon 635 Capitol Street NE Salem, OR 97301 Department of Agriculture, 503-986-4621 www.oregon.gov/ODA/programs/Weeds/Pages/Default.aspx Bugwood.org March 2016