Effective Herbicides for Controlling Central Coast Rangeland Weeds

Do you have yellow starthistle, Italian thistle, Himalaya blackberry, white top, or other common Central Coast rangeland weeds on your ranch? If so, you may be wondering which herbicides are most effective, how much they cost, what is required to purchase and spray a particular herbicide, when to spray, whether the herbicide affects grasses or clovers, and if the herbicide is safe for your livestock and pets. Many Central Coast rangeland landowners have been asking these same questions. So, I compiled this information in two tables. Table 1 shows some of our common rangeland weeds and different herbicide treatment options. Table 2 lists six of the most commonly used rangeland herbicides, and answers questions about cost, when to spray, purchasing requirements, affected plants, and grazing/pet restrictions. Both tables are attached as PDFs at the bottom of this blog post. All of this information is already available from a variety of sources, but I have put it together in two easy to use reference tables. The tables are self-explanatory for the most part, but the information below may clarify a few things.

Integrated Pest Management (IPM)

IPM is a weed management approach that uses multiple control methods. Control methods could include mechanical control, manual control, grazing, seeding, herbicide, etc. The most effective options will depend on the particular species you are trying to control. This blog post focuses on herbicide because I am often asked about chemical treatment options. However, your weed control efforts will likely be most successful if you use a variety of methods.

Operator ID's, Restricted Materials Permits, & Private Applicator Certificates

Most of the herbicides in Table 2 are general use pesticides, meaning that you only need an operator ID to purchase and use them (Carbonaro, pers. comm.). Operator ID's are free and can be obtained from your County Agricultural Commissioner's office. No test is required. But, you'll need to show a property map in order to get your operator ID.

One herbicide in Table 2, 2, 4-D, is a California state restricted pesticide when applied on rangelands. Before you can purchase or spray California state restricted pesticides, two things are required: a Private or Commercial Applicator Certificate and a restricted materials permit. You can get a Private Applicator Certificate from your County Ag Commissioner's office. This requires taking a free test. The test is based on Pesticide Safety: A Reference Manual for Private Applicators, 2^nd Ed., published by the University of California. This book can be purchased from most County Ag Commissioner or UC Cooperative Extension offices or online at: http://anrcatalog.ucanr.edu/Details.aspx?itemNo=3383. Once you have your Private Applicator Certificate you'll be able to obtain a restricted materials permit, again from your County Ag Commissioner's office. Alternatively, you can hire a licensed pest control business to purchase and spray California state restricted pesticides.

Read Labels, Follow Federal, State & Local Regulations, and Report Pesticide Use to Your County Ag Department

Although Table 2 includes information from the herbicide labels, it is not a substitute for reading the entire herbicide label before you spray (Carbonaro, pers. comm.). Always read the label before using any of these herbicides. In California, in addition to following the label, applicators will also need to follow federal, state, and local regulations. And, remember that you should submit a pesticide use report to your County Agricultural Commissioner's office for all pesticides used on rangelands.

For additional information about weeds and how to manage them, check out this website: http://wric.ucdavis.edu. The Invasive Thistles of Bay Area Counties & Herbicides for Controlling Thistles Handout compiled by Guy Kyser, UC Cooperative Extension Specialist in Weed Science at UC Davis is a great resource and is attached at the bottom of this blog post.

References

Carbonaro, D. 2017. Personal communication, 4/16/2017. Carbonaro is a Senior Biologist/Inspector with the San Benito County Agricultural Commissioner's Office.