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Do Something about Yellow Starthistle

In 2009, the California Department of Food and Agriculture (CDFA) announced almost $2.1 million in American Recovery and Reinvestment Act (stimulus) funds for targeted invasive weed projects. These projects are focused on weed population detection, risk assessment, and rapid response. The purpose is to protect California’s valuable forested lands.

Many California counties and other agencies, such as the California Conservation Corps, the California Association of Resource Conservation Districts, Ducks Unlimited, and the California Invasive Plant Council, among others, have applied for and received funding for weed management projects in 2010. You can access the list of counties’ and agencies’ projects at http://www.cdfa.ca.gov/Recovery/ARRA_Projects.html

One project impacting our local residents is the Yellow Starthistle Leading Edge project. Managed by University of California Cooperative Extension (UCCE), the project is designed for “controlling Yellow Starthistle (Centaurea solstitialis) and stopping the spread at the eastern leading edge in the Sierra Nevada foothills thereby protecting 12.9 million acres of forested lands, including wildlife habitat, timber production, habitat for endangered and threatened plant and animal species, and the unique recreational assets of the Sierra Nevadas.”

What does this have to do with you? Tuolumne County’s UCCE office is currently mapping, using GPS technology, resident populations of yellow starthistle in eastern and higher elevation areas of the county. Neighborhoods where yellow starthistle is advancing will be invited to workshops offering information and techniques to control the spread of this spiny, unpalatable-to-livestock, noxious weed.

What’s wrong with yellow starthistle? Yellow starthistle infests between 10 and 15 million acres in California! It depletes the ground of soil moisture (it loves hot, dry areas) preventing other plants from growing. It forms dense stands that are difficult to walk through. It’s poisonous to horses, causing fatal “chewing disease.” Its seeds can remain viable in the soil for longer than three years.

What can you do?
• Hand pull small infestations. Do not throw the plants into the garbage can or compost pile. Put them in double black garbage bags and place the bags in the sun for six weeks to kill the plants. Pull some more.
• Purchase only certified seed for lawns and pastures.
• Hay bales may be contaminated. Carefully check hay for evidence of yellow starthistle. Place hay bales in one area and check the area periodically for yellow starthistle growth. Remove any young plants you find.
• Livestock pastured in yellow starthistle-infested areas should not be moved to other areas.
• When driving through areas infested with yellow starthistle, check vehicle tires to make sure you’re not transporting seed.
• Because yellow starthistle is so competitive, once it’s removed it’s important to reseed areas with fast growing species such as wildflowers or bunchgrasses.

It’s the wrong time of year to mow yellow starthistle. Most of it has already flowered and set seed. For that same reason, it’s also the wrong time for herbicide treatment, which should come during the winter rains (preemergent) or after seedlings have emerged in the spring (postemergent).

However, it’s not too late to hand pull some of those ugly weeds and, over the next few months, look for your invitation to a yellow starthistle control workshop.

Rebecca Miller-Cripps is the program coordinator for the UCCE Tuolumne County Master Gardener program.