UPPER SALINAS LAS TABLAS
RESOURCE CONSERVATION DISTRICT
65 Main Street, Suite 107
(805) 434 0396, ext 5
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March 8, 2010 Dear Landowner. The highly invasive Yellow Starthistle (YST) has now spread over more than 15 million acres in California, covering rangelands, forests, wildlife habitat and roadsides. The state spends up to 80 million dollars annually in weed control with an additional $ 7.6 million in out of pocket expenses to landowners. YST has spread throughout San Luis Obispo County. It is a threat to rangeland and grain fields, is toxic to horses, causes injury to humans and consumes our valuable water resources. We believe that these serious economic and environmental costs must prompt each of us to become actively involved in controlling Yellow Starthistles on our properties and roadside right-of-ways where traffic conditions permit it. We would like to assist you in those efforts by providing you with some of the most frequently asked for information on Yellow Starthistle. This community outreach effort is supported by and funded with the assistance from Supervisors Jim Patterson, District V and Frank Mecham, District I. YST is an annual, dying after seed maturity usually in late May to mid June. One large plant can produce as many as 70,000! viable seeds which begin germinating with first rains. However, many seeds can remain dormant in the soil for 3 or more years before germinating, which requires that control efforts be done for several years. YST can be identified at a young state by it’s somewhat flat-to-the ground, tender, lobed leaves, which at that stage also show the plant’s characteristic light to bluish green color at the center where new growth occurs. As the plant grows, it forms single or multiple stalks, lobed leaves and the bluish green color which can be readily seen when other vegetation turns brown. Formidable spines begin to form at the base of each flower head around May. Once the bright yellow flowers begin blooming they quickly produce seeds and within 10 to 16 days, seed maturity and reseeding begins. After the plant dies, flower heads turn into small white cotton-like tufts in the fall, which usually remain on the dead plant skeleton through the winter and can help you identify locations of new seedlings the following spring. It is critical to be familiar with the life cycle of this weed, since that determines what control methods to use and when.
CONTROL METHODS:Because of this year’s abundant rainfall, YST germinated with first heavy rains and also subsequent months. The difference in stages of growth and competing tall vegetation will have to be considered in your control this year. Hand-pulling; hoeing; shoveling, any of these must ensure removal of at least 2-3″ of root. Mowing: There is only a small window of opportunity to effectively use mowing as a control tool. It should be done when the flowers are just beginning to appear and before they have a chance to produce seeds. Earlier mowing opens the plant to much loved sunlight and will promote re-growth. Repeated mowing will eventually keep the plant below mower blades. Grazing: YST is toxic to horses. Cattle will avoid YST when the spines have formed but graze it well’ till then. As an YST control method, cattle should intensely graze infested fields for short periods in a field rotation plan, avoiding overgrazing of desirable vegetation. Spraying: The herbicide MILESTONE specifically targets YST, leaving grasses and many other plants untouched. It does kill filaree, clover and can harm oak seedlings. MILESTONE is most effective when the plants are younger and requires stronger concentrations as the plant grows taller. It is not effective when the plant is mature at the flowering stage. TRANSLINE is another YST specific herbicide. These products are available at local agricultural supply stores. The label requirements must be strictly followed when using these – and other -herbicides. Additionally, Transline and Round Up should not be used within 50 feet of a water body, creek or riparian area. Milestone may be used up to the edge of a water body but cannot be sprayed in standing water. Check label carefully. ROUNDUP: can be an effective tool for spot spraying small infestations. It may be desirable to re-seed areas sprayed with Roundup, using native grasses, to minimize re-introduction of weeds into bare spots. Biological control: the YST host specific Hairy Weevil and False Peacock Fly were introduced into the west, including our county, several years ago and have been found to have spread well but are not capable of controlling present high infestations. With funding thank you for doing your part to control this Contact information Websites:
Upper Salinas Las Tablas RCD 805-434-0396, ext 5
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