Control and Prevention of Noxious Weeds
Controlling weeds poses a special dilemma because once a weed infestation is identified, it is often already so extensive that containment is difficult and expensive. Biological control (using organisms such as insects) is effective in slowing the spread of weeds but generally cannot eradicate the infestation. Manually pulling weeds or using machines to dig them up is effective with smaller infestations if done carefully to avoid spreading seeds. Herbicides can be effective in controlling weeds and stopping their spread especially when infestations are detected early. Land managers generally take an integrated approach, using a combination of these methods.
Here is what you can do to help prevent the spread of noxious weeds:
- Refrain from picking wildflowers or plants; they may be noxious weeds and picking them can spread their seeds
- Do not camp in or hike through weed infested areas; stay on designated trails
- Clean all camping gear, clothing, and shoes before leaving an area to avoid inadvertently taking seeds along to the next campsite, county, or state
- Check with your local nursery or nature center before adding plants to your garden. Some varieties come in a hybridized or non-invasive variety
- Check with your local rangers or land managers before starting a backcountry hike. Find out how to identify problem weed species in the area so you can report any infestations you may encounter
- Drive only on established roads or trails away from weed infested areas. Seeds can become imbedded in tire treads and travel to new areas
- For pack animals, use only feed that is certified weed free starting 96 hours before entering backcountry areas
- Remove weed seeds from the animals by brushing them thoroughly and cleaning their hooves.
Hollister Field Office Weed Control Projects
Yellow Star Thistle
The yellow starthistle (YST) control project is ongoing since 2005. The YST project was initiated to improve wildlife habitat and to lessen the impact of this noxious, invasive species on federally-listed threatened San Benito evening primrose (Camissonia benitensis). San Benito evening primrose grows on serpentine alluvial deposits adjacent to Clear Creek and yellow starthistle was beginning to invade that habitat. San Benito evening primrose has re-emerged in some areas where YST has been controlled.
The YST project area includes the entrance to the Clear Creek Management Area near the intersection of Coalinga Road-Clear Creek Road (R1) (approximately 75 acres) and includes about 15 acres in the Upper Sweetwater area near the BLM campground.
Treatments within the YST project area have included manual removal (hand pulling), mowing (weed eaters, mower), herbicide application (ATV ground application), and prescribed fire. The most effective treatment has been alternating prescribed fire in June (kills adult plants and burns out thatch) and Transline (clopyralid) herbicide application in February/March. YST is now nearly eradicated from the project area.
The tamarisk control project is ongoing since 2006. The tamarisk control project was initiated to improve riparian zone habitat quality for wildlife. The tamarisk control project area includes Panoche Creek and Silver Creek and is approximately 800 acres in size.
Tamarisk control methods have included: brush mowing and cut stump application of Roundup (glyphosate) herbicide in 2006; basal bark application of Garlon4 (triclopyr) to resprouts using backpack sprayers in 2007 and 2008; foliar application of Aquamaster (glyphosate) with a boom attached at an elevated position on a small caterpillar in 2010; and most recently aerial application of Habitat (imazapyr) and Aquamaster (glyphosate) herbicide with a helicopter in 2011. The aerial herbicide application by helicopter has proven to be the most efficient and effective control method for the species.
Some general guidelines for preventing weeds from entering public lands and spreading to new uninfested areas:
- Collect seed on the land and use local native seeds for planting
- Commercial seed should be required to be free of noxious weeds and labeled accordingly
- Consider seeding only in graded areas or areas where damage will occur, such as erosion, if seeding is not done
- When constructing or maintaining roads, inspect gravel pits and fill sources to identify weed-free sources
- Equipment or machinery should be cleaned before it is moved from a noxious-weed contaminated area to a noncontaminated area