Yellow Star Thistle Control in Vineyards

Yellow Star Thistle (YST) is a noxious weed that inhabits many of our vineyards and surrounding landscape. It has been very difficult to control and can overcome a vineyard or field very quickly. Its spread can be very vigorous and overcome an area in a matter of two years. We understand that this weed is not always considered an economic pest in our vineyards, but it is definitely a nuisance and it is an economic pest in rangeland situations. With the reduced rainfall in 2007 the seed count is very low and this year there is a good opportunity to gain control of this noxious weed.

There are a few steps to en effective treatment plan:
1. Survey your property and identify areas with populations of YST. Encourage your neighbors to do the same.
2. Develop and spray or a mechanical cultivation program to treat the weeds before they get too big. Spray equipment can be shared or expenses split between neighbors.
3. Follow up in April and early May to re-spray areas that were missed.
4. Finally, some hand hoeing might be necessary to eliminate any mature plants that have gone to seed. It is extremely important to eliminate all mature plants, because the seeds from one plant this year can produce up to 100 plants next year.

Information on treatment and control can be reached at the following locations:
1. Your Local Farm Chemical Dealer
2. County Agricultural Commissioner 781-7910
3. Rex Swan- SLO Cattleman’s Association 674-3077
4. Mark Battany- UC Cooperative Extension (mcbattany@ucdavis.edu) 781-5948
http://cesanluisobispo.ucdavis.edu/Viticulture/Yellow_Starthistle.htm