Three species of insects have been introduced as biological control agents of tansy ragwort in California: a flea beetle (Longitarsus jacobaeae, Coleoptera: Chrysomelid), thecinnabar moth (Tyria jacobaeae, Lepidoptera: Erebidae) and the ragwort seed head fly (Botanophila seneciella, Diptera: Anthomyiidae). The flea beetle has the most impact on reducing abundance of the weed, but the cinnabar moth provides some additional control. The seed head fly has not established in California.

The flea beetle and moth have been highly effective at reducing tansy ragwort populations in California and Oregon, reducing it by up to 99% in ungrazed areas. The estimated benefit-to-cost ratio of this project in Oregon is about 14:1, with annual benefits of $5 million per year (in 1993). Biological control alone does not provide control of tansy ragwort in grazed pastures. Experiments have shown that both the insects and plant competition contribute to reduction of tansy ragwort. Both insects are good dispersers. Disturbances that cause seed in the soil seed bank to germinate lead to temporary resurgence of the weed, which is then controlled by insects in 1 to 3 years.

The flea beetle has one generation per year (Fig. 1). Adults feed on foliage creating small shot holes, and lay eggs around the bases of rosettes. Larvae feed inside leaf petioles and the root crowns causing extensive damage and sometimes plant death. Three flea beetle biotypes have been introduced that differ in their biology. The Italian CPNW biotype (= Coastal Pacific Northwest) is adapted to regions with mild winters and dry summers. Adults aestivate during the summer and begin feeding and laying eggs in the fall after precipitation begins. Eggs can be laid throughout the winter, and larvae continue developing until spring. Pupation occurs in the soil, and adults emerge in the spring and feed briefly before aestivating during summer. The Italian CAD biotype (=cold adapted) is adapted to regions with colder temperatures and humid summers. Larvae continue feeding into the summer, pupation occurs in midsummer, and adults emerge in late summer. The Swiss biotype is adapted to regions with even colder winters and humid summers. Adults lay eggs in summer and fall, but eggs do not hatch until the spring. Larvae develop in spring, pupate in early summer, and adults emerge in summer. All the biotypes appear to perform best in dense infestations at sunny sites that are not seasonally flooded. The Italian CPNW biotype has been very successful in California, whereas the Italian CAD biotype has done better in the Cascade Mountains and Intermountain West up to about 1,300 ft elevation. The Swiss biotype does well at higher elevations, up to about 5,500 ft. No non-target plant effects have been reported for any of these biotypes.

The cinnabar moth has one generation per year (Fig. 2). Adults lay clusters of eggs on the underside of leaves. The orange-and-black-banded larvae are conspicuous and feed on the leaves and shoots in spring and summer (Fig. 3). Pupation occurs in the soil, and adults emerge the following spring. Although larvae can completely defoliate plants, they are often able to leaf out again later in the year after the onset of fall precipitation. Insect predators, parasites and a microsporidian disease can limit the effectiveness of the moth. In Oregon, the cinnabar moth has been reported to develop on some native non-target plants, including Senecio triangularis and Packera pseudaurea. Non-target use of these plants in California has not been observed.

Biological Control Agents


Common name




Botanophila seneciella
(=B. jacobaeae)

ragwort seed head fly

failed to establish


first released in CA in 1966

Tyria jacobaeae

cinnabar moth



first released in CA in 1959

Longitarsus jacobaeae
(=L. flavicornis)

tansy ragwort flea beetle



first released in CA in 1969

How the Technique Is Employed

If biological control agents are already present at your site there is no need to release more. Look for signs of insects and their damage. During summer, look for orange-and-black-banded caterpillars and/or defoliation caused by the cinnabar moth. Adult moths have a conspicuous red and brown wing pattern. In the fall or spring, look for shot holes in leaves caused by adults of the flea beetle, or split open rosettes to look for root crown damage.

Cinnabar moth larvae can be collected in the summer by tapping plants to make larvae fall into an open container. Larvae that have pinkish-colored feces are probably infected by a Nosema pathogen and should not be collected for redistribution.

Collect adult flea beetles by sweep net or insect vacuum (D-Vac), in the fall for the Italian CPNW biotype or summer for the others. Look for rosettes that have shot holes in the leaves.

For additional details see Winston et al (2011).

Special Tips

Knowing what insects are present may help you to integrate other management strategies. The flea beetle larvae feed in the fall to early spring in California whereas the moth caterpillars feed during summer.

The flea beetles oversummer in sheltered places, such as in tree bark, under rocks in leaf litter and even in house attics.

Biological control of tansy ragwort has been most successful in ungrazed areas.


Mowing during summer will probably kill the cinnabar moth caterpillars and deprive them of foliage to eat.

Herbicides that kill tansy ragwort will deprive the insects of the ability to reproduce. However, the insects will search for the remaining plants that have not been killed. Thus, biological control can be complementary to herbicide or other control treatments, especially if there are areas that escape the treatment (too difficult to access or too environmentally sensitive to treat).

In Oregon, the cinnabar moth has been reported to develop on some native non-target plants, including Senecio triangularis and Packera pseudaurea. Non-target use of these plants in California has not been observed so there are no restrictions on its use in CA.

No non-target plant effects have been reported for the flea beetle. A similar flea beetle, Longitarsus ganglbaueri, occurs on tansy ragwort in CA, OR and WA, and is an accidentally introduced alien species that feeds on some native plants, including Packera pseudaurea.

Where Can I Get These?

Collect adult flea beetles by sweep net or insect vacuum in the fall. Look for rosettes that have shot holes in the leaves.

The flea beetle and cinnabar moth may be available from your county Agricultural Commissioner.


Coombs, E.M., P.B. McEvoy and G.P. Markin. 2004. Tansy ragwort. In: E.M. Coombs, J.K. Clark, G.L. Piper and A.F. Cofrancesco, Jr. (eds.), Biological Control of Invasive Plants in the United States. Oregon State University Press, Corvallis, OR. pp. 335-344.

McEvoy, P.B. and N.T. Rudd. 1993. Effects of vegetation disturbances on insect biological control of tansy ragwort, Senecio jacobaea. Ecological Applications 3: 682-698.

Turner, C.E. and P.B. McEvoy. 1995. Tansy ragwort. In: J.R. Nechols, L.A. Andres, J.W. Beardsley, R.D. Goeden and C.G. Jackson (eds.), Biological Control in the Western United States: Accomplishments and Benefits of Regional Research Project W-84, 1964-1989. University of California, Division of Agriculture and Natural Resources, Oakland. Publication No. 3361, pp. 264-269.

Pemberton, R.W. and C.E. Turner. 1990. Biological control Senecio jacobaea in northern California, an enduring success. Entomophaga 35: 71-77.

Winston, R., C.B. Randall, J.L. Littlefield, M. Schwarzländer, J. Birdsall, and E.M. Coombs. 2011. Biology and Biological Control of Tansy Ragwort. USDA ForestService, FHTET-2011-02.

Contributing Authors

Dr. Michael J. Pitcairn, Program Manager, California Department of Food and Agriculture

Dr. Lincoln Smith, Research Entomologist, USDA.