News Release
California Department of Food and Agriculture
Media Contact:
Steve Lyle, Office of Public Affairs, (916) 654-0462,
Release #03-047

SACRAMENTO – The California Department of Food and Agriculture’s Biological Control Program is embarking on a pilot project aimed at controlling an invasive weed known as yellow starthistle, which infests approximately 14 million acres in California.

While yellow starthistle is an attractive plant that sprouts bright yellow flowers, it also forms dense spiny thickets that destroy grassland for cattle and wildlife, and prevent entry by humans and animals.

CDFA biologists have found a natural pathogen of yellow starthistle in its native range in the Mediterranean region of Southern Europe. Puccinia jaceae is a naturally occurring fungus that causes a disease in yellow starthistle commonly known as rust due to the rust-colored pustules that develop on infected plants. 

Previously, CDFA had introduced insects from the Mediterranean regions that feed on the plant, but the impact was not significant enough to establish control.

Extensive greenhouse testing has shown that the rust is specific to yellow starthistle, and that it cannot infect the nearly 100 species of crops and native plants that were tested.

Initial releases of the rust have occurred in an isolated valley in Napa County. It may take several years to establish its effectiveness.


Note to editors-

CDFA biologists will join representatives from the USDA and the Napa County Agricultural Commissioner’s office for a media availability on Wednesday, July 30, at 10a.m., at Mead Ranch in Napa County.

Mead Ranch is on Atlas Peak Road, which can be reached by taking Highway 121 east out of Napa. Follow Atlas Peak Road for approximately 7 miles in a northbound direction and look for the signs.  



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California Department of Food and Agriculture Office of Public Affairs
1220 N St., Ste. 214, Sacramento, CA 95814