Integrated strategies for the attrition of yellow starthistle on northern California rangeland

摘要

Over the past 30 years, yellow starthistle (Centaurea solstitialis L.) has become a serious threat to California grasslands. Recent 1996-1998 CDFA surveys have estimated that roughly 40 percent of the townships in California have some level of infestation, with potential acreage estimates of 12 million acres (Pitcairn et al. 1998). Yellow starthistle control strategies have included chemical (DiTomaso et al. 1999b), classical biological control (Balciunas and Villegas 1999), burning (DiTomaso et al. 1999a), mowing (Benefield et al. 1999), and grazing (Thomsen et al. 1993). Each of these strategies alone may reduce total seed production. However, the inherent issue in dealing with yellow starthistle lies in its ability to readily reinvade annual grasslands following successful control. Therefore, any short- term management plan will likely fail given enough time. A successful long-term management plan must attempt to address the issue of reinvasion following control. The current paradigm in California and much of the Western United States suggests that reestablishing perennial grasses is a sustainable long-term strategy for preventing or suppressing noxious weed invasion (Sheley et al. 1996). However, this paradigm has not been widely tested. Weinitiated a long -term experiment in 1997 using an integrated system with the herbicide clopyralid and the perennial grass pubescent wheatgrass to test this idea. The focus of this paper is an update on the experiment following three years of treatment.