Centaurea melitensis (Malta starthistle, tocalote)

Centaurea melitensis

Photo courtesy Joseph DiTomaso

Centaurea melitensis (Malta starthistle, tocalote) is a bushy annual (family Asteraceae) found throughout most of California and in many other western states. Malta starthistle prefers disturbed and open areas, including grasslands, open woodlands, agricultural fields and roadsides. It is most invasive in California’s central western and southwestern regions. While Malta starthistle is less invasive than yellow starthistle (Centaurea solstitialis), but it still spreads quickly by producing great quantities of seed if given the proper conditions. Insects such as the false peacock fly (Chaetorellia succinea) and hairy weevil (Eustenopus villosus) have been used as biological controls with some success.

Cal-IPC Inventory rating: Moderate

Cal-IPC Resources on Centaurea melitensis

• California Invasive Plant Inventory Assessment Form (pdf) - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.
• Species account from Invasive Plants of California's Wildlands - Includes biology and management information.
• Cal-IPC News - Articles from our quarterly newsletter. Each issue is available as a pdf. List of articles on Centaurea melitensis.
• Cal-IPC Symposium Proceedings - Presentations and papers from our annual Symposium. List of articles on Centaurea melitensis.
• California distribution map - Maps based on survey data from county Weed Management Areas. These maps are the product of those working in the field and are not intended to be definitive.

Cal-IPC News Articles

• O'Rourke, B. and J. Horenstein (2009). Tackling invasive plants on California Sept. of Fish & Game lands. Cal-IPC News. 17: 12.
• DiTomaso, J. (1998). Results of the CalEPPC questionnaire at Symposium '98 in Ontario. CalEPPC News. 6: 4.
• Kelly, M. (2000). Education: Wildland weed tours and talks. CalEPPC News. 8: 3-4.

Cal-IPC Symposium Proceedings

• Archbald, G. (1998). Mechanical control methods: beyond weed bashing. California Exotic Pest Plant Council Symposium '98. Ontario, CA.
• Burrascano, C. (2001). Review of the impact of invasive weeds on two endangered plant species: Acanthomintha ilicifolia (San Diego thornmint) and Monardella linoides ssp. viminea (willowly monardella). California Exotic Pest Plant Council Symposium 2001. San Diego, CA.
• Butler, E. and S. Britting (1998). Mapping and control of weeds in the American River Parkway. California Exotic Pest Plant Council Symposium '98. Ontario, CA.
• DiTomaso, J. M. (1995). Overview of extension non-crop weed research in California. California Exotic Pest Plant Council Symposium '95. J. Lovich, J. Randall and M. Kelly. Pacific Grove, CA.
• DiTomaso, J. M., C. Benefield, et al. (1998). Reproductive biology of yellow starthistle (Centaurea solstitialis) maximizing late season control. California Exotic Pest Plant Council Symposium '98. Ontario, CA.
• DiTomaso, J. M., G. B. Kyser, et al. (1998). Prescribed burning for control of yellow starthistle (Centaurea solstitialis) and enhanced native plant diversity. California Exotic Pest Plant Council Symposium '98. Ontario, CA.
• Giessow, J. and P. Zedler (1996). The effects of fire frequency and firebreaks on the abundance and species richness of exotic plant species in coastal sage scrub. California Exotic Pest Plant Council Symposium '96. San Diego, CA.
• Marler, M. J. and R. M. Callaway (2000). Role of mycorrhizae in Centaurea invasions. California Exotic Pest Plant Council Symposium 2000. Concord, CA.
• Northam, F. E. (2001). Invasive plant species management in Arizona. California Exotic Pest Plant Council Symposium 2001. San Diego, CA.
• Rusmore, J. T. (1995). Use of fire and cutting to control yellow starthistle. California Exotic Pest Plant Council Symposium '95. M. Kelly and J. Lovich. Pacific Grove, CA.
• Young, J. A., C. D. Clements, et al. (2000). Purple starthistle seed germination. California Exotic Pest Plant Council Symposium 2000. M. Kelly. Ontario, CA.

Other Resources on Centaurea melitensis

• USDA PLANTS database - Federal database with information on identification and distribution, and links to websites in individual states.
• Jepson Online Interchange for California Flora - Information on taxonomy, biology, and distribution from the UC Berkeley Jepson Herbarium.
• CalFlora - Distribution information by county based on submitted observations and herbarium specimens.
• The Nature Conservancy Management Summary - Information compiled by TNC land managers. Photos included for some species.
• CalPhotos - Images of plants taken mostly in California.
• Natural Resource Projects Inventory - State database with information on resource management projects throughout California. Query by the species of interest.

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