Along scenic corridors, county roads and state highways of the foothills of the Sierra Nevada mountain range, weeds—especially yellow starthistle and Italian thistle—are creating solid stands of invasion that defy control.
The California Department of Transportation (CalTrans) manages over 15,000 miles of roadway and over 230,000 acres of right of way. Along state highways CalTrans manages a narrow easement strip on either side of the roadway for vegetation control. According to CalTra
However, in many areas, there is visible evidence of roadside weed control. Mastication removes brushy and woody growth; chemical spray and mowing removes grasses. But the problem lies between the edge of CalTrans easements and property owners’ boundaries. It is apparent that weed control is not performed in the “no-man’s land” between easement and fence line.
Many farmers, ranchers and growers are conscientious about treating weeds such as yellow starthistle; many continue to be weed warriors even in the face of severe state and county budget cuts that undermine public weed control programs. Pastures and fields along foothill roads such as California State Highway 49 and cross-Sierra roads such as 108 and 88, show signs of consistent weed control on private property. However, just across the fence may stand a solid growth of yellow starthistle or Italian thistle that is not being controlled.
These uncontrolled patches provide a seedbank for future weed populations and threaten to invade areas that are being privately controlled.
According to U.C. Integrated Pest Management (IPM) guidelines for yellow starthistle control: “Yellow starthistle proliferates along roadsides. Invasion by this weed may be increased with disturbances created by road building and maintenance. Seeds are often spread by vehicles or with the transportation of livestock or contaminated soil…Mowing can be used to manage yellow starthistle, provided it is well timed and used on plants with a high branching pattern.”
Unfortunately, weed control techniques used along roadways may not comply with these guidelines. As an example, dense stands of yellow starthistle occurring along California State Highway 120 (on the way to Yosemite National Park) were mowed by CalTrans as part of their highway vegetation management program. According to U.S. Forest Service personnel, mowing was done after the plants had set seed; not only was mowing ineffective as a control method at that stage of the plant's life, but viable seeds were picked up by mowing equipment and transported to other sites due to lack of equipment cleaning procedures.
What is the answer to this weed-control dilemma? Public agencies and private landowners need to communicate, working together to create collaborative weed control practices that treat ALL populations of noxious weeds occurring in an area. Weed control is not effective when limited to narrowly-defined jurisdictions.