Weed Biological Control Projects

Project: Bull thistle (Cirsium vulgare (Savi))
Principal Investigator: Baldo Villegas
Cooperators: Eric Coombs, Oregon Department of Agriculture; Anita Sauber, Marin County Department of Agriculture; Humboldt County Department of Agriculture; Larry Allen, San Joaquin County Department of Agriculture; Dennis Haines, Tulare County Department of Agriculture
Summary: Efforts are underway to introduce the bull thistle gall fly, Urophora stylata, into California. Releases have been made in 1993-1995 in El Dorado, Marin, Mendocino, Modoc, Shasta, San Luis Obispo, and Tulare Counties but was recovered the following year at only one site in Marin County. Additional releases were made in 1997 and 1998 in Humboldt, Marin, San Joaquin and Tulare Counties. In Fall 1998, U. stylata was recovered at all 1997-98 release sites. Monitoring of sites will be performed in 1999.
Project: Diffuse Knapweed (Centaurea diffusaLamarck)
Principal Investigator: Don Joley
Cooperators: Dale Woods, BC Program, CDFA
Summary: Diffuse knapweed is an A-rated noxious weed currently under eradication by the California Department of Food and Agriculture. However, eradication efforts are prevented at one site in the Trinity Mountains in Northern California. Several insects have been established at this site in an attempt to reduce reproduction of diffuse knapweed and reduce the amount of seed leaving this area. All diffuse knapweed outside this area is eradicated, thus containing the spread of this weed. To date, four biological control agents, Urophora affinis, Sphenoptera jugoslavica, Bangasternus fausti, and Larinus minutus, have become established. Current efforts are to monitor population increase and impact of these insects at this site.
Project: Spotted Knapweed (Centaurea maculosa Lamarck)
Principal Investigator: Dale Woods
Cooperators: Don Joley, BC Program, CDFA
Summary: Spotted knapweed is an A-rated noxious weed currently under eradication by the California Department of Food and Agriculture. However, eradication efforts are prevented at one site along the Pit River in Shasta County in Northern California. Efforts are underway to establish several insects at this site in an attemp to reduce reproduction of spotted knapweed and reduce the amount of seed leaving this area. All spotted knapweed outside this area is eradicated, thus containing the spread of this weed. To date, five biological control agents, Urophora affinis, Terellia virens, Larinus minutus, Agapeta zoegana, and Cyphocleonus achates, have become established. Current efforts are to monitor population increase and impact of these insects at this site.
Project: Squarrose Knapweed (Centaurea squarrosa Willd.)
Principal Investigator: Dale Woods
Cooperators: Don Joley & Baldo Villegas, BC Program, CDFA
Summary: Squarrose knapweed is closely related to both diffuse and spotted knapweeds. Although most populations of this noxious weed are actively under a chemical control program, the Biological Control Program is testing the acceptance of several biological control insects used on diffuse and spotted knapweeds for this weed at two sites. Pre-release surveys showed that both Urophora quadrifasciata and U. affinis has moved on their own from neighboring states and infest this weed at one site in Siskiyou County. Three biological control insects have been release against squarrose knapweed in northern California: Cyphocleonus achates, Bangasternus fausti, and Larinus minutus. Only B. fausti has been recovered to date. Efforts will continue to monitor release sites for recoveries and to release other biological control insects.
Project: Purple Loosestrife (Lythrum salicariae L.)
Principal Investigator: Don Joley and Baldo Villegas
Cooperators: Eric Coombs, Oregon Department of Agriculture; Harrie Riley, Butte County Agriculture Department; Eric Gunderson, Nevada County Agriculture Department; Tony Linegar, Shasta County Department of Agriculture
Summary: Efforts are underway to establish several insect natural enemies on purple loosestrife in California. The root beetle, Hylobius transversovittatus, was released in 1996 and 1997 in Butte and Shasta Counties in northern California, but has not been recovered to date. The flower bud weevil, Nanophyes marmoratus, was released in 1997 in Butte and Shasta Counties but also has not been recovered. Two leaf-feeding beetles, Galerucella calmariensis and G. pusilla, were released at five? sites in five counties in 1998. These beetles were recovered at all release sites a couple of months following the release. In 1999, surveys will be performed to determine overwintering survival of these beetles.
Project: Gorse (Ulex europaeus L.)
Principal Investigator: Baldo Villegas
Cooperators: Eric Coombs, Oregon Department of Agriculture
Summary: Efforts are underway to establish several biological control agents on gorse in northern California. The seed weevil, Exapion ulicis, was established in California in the 1970's. In 1994, the spidermite, Tetranychus lintearius, was released in Humboldt, Marin, Marin and Sonoma Counties. The mite has established in three of the counties but exists at low levels. Monitoring efforts continue to determine population levels and dispersion away from release sites.
Project: Scotch Thistle (Onopordum acanthium L.)
Principal Investigator: Mike Pitcairn and Don Joley
Cooperators: Dale Woods, BC Program, CDFA
Summary: The USDA-ARS, Albany, is performing host specificity tests on several potential biological control agents for Scotch thistle. Many of the test plants are being grown by CDFA our Meadowview facility. This cooperative project will continue until all potential bioagents are tested. In addition, a field study is underway at two sites in Modoc County to obtain demographic data on births, deaths, and growth habit of Scotch thistle.
Project: Russian Thistle (Salsola tragus L.)
Principal Investigator: Mike Pitcairn
Cooperators: Rouhollah Sobhian, USDA-ARS, Montpellier, France; Richard Goeden and Sergei Triapitsyn, University of California, Riverside.
Summary: Efforts are underway to search for new biological control agents on Russisn thistle in Europe and Asia. This work is being funded by CDFA and performed by Rouhollah Sobhian, USDA-ARS, European Biological Control Laboratory, located in Montpellier, France, and Richard Goeden and Sergei Triapitsyn, University of California, Riverside. To date, at least five potential biological control agents has been found: Lixus salolae (a weevil), Aceria salsoli (a mite), Gymnancella sp. (a moth), Piesma salsolae (a plant bug), and Uromyces salsolae (a rust fungus).

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Information last updated: March 2,2000