Managing yellow starthistle on rangeland
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Authors: C. D. Thomsen, W. A. Williams, M. R. George, W. B. McHenry, F. I. Bell, and R. S. Knight
Date: 1989
Journal: California Agriculture
Volume: 43
Number: 5
Pages: 4-7
Summary of Methods: The effects of cattle grazing alone and grazing paired with herbicide application on yellow starthistle, ability of annual and perennial grasses to suppress yellow starthistle through competition, and reduction of yellow starthistle through timed defoliation were examined at two sites in California over a three year time period (only one year has been completed). The first site was 20 miles southwest of Red Bluff and the second site was located 20 miles west of Maxwell, CA. Sites were grazed early and late in the growing season; Herbicide applications of 2,4-D were applied during the rosette stage just before bolt. Cattle were stocked at 40-100 cows per acre with various grazing periods of 2.5-24 hours to influence intensity, which was classified as light, moderate and heavy.
Article Summary / Main Points: • Environmental conditions did not allow the effects of grazing on the competitive ability of other species to be determined. • Late season grazing did not affect the density of yellow starthistle it reduced plant height, canopy cover and seed production. • Late grazing also had a 20% mortality rate and an estimated 75% reduction in canopy cover for the weed, but most plants were resilient enough to regrow by expansion of basal and axillary shoots. • Grazing combined with herbicide decreased yellow starthistle densities by an average of 6 plants per square foot. Though this effect was limited on half of the plots due to late season rains that favored yellow starthistle and allowed for it recover in these plots.
Vegetation Types: California Grasslands (including all annual grasslands) Intermountain Grasslands (includes Palouse Prairie and Canyon Grasslands) Oak Woodlands Ponderosa Pine Woodlands
MLRA Ecoregions: 17 Sacramento and San Joaquin Valleys
Agrovoc Control Words: Noxious Weeds Rangelands Grazing
Article Review Type: Peer Reviewed
Article Type: Experimental Research
Keywords: plant size, plant canopy, plant mortality, plant density, weed management, centaurea solstitialis, grazing, herbicide treatment, targeted grazing
Annotation: These results were classified as preliminary results and based on only one year of data. With the increased expansion of yellow starthistle territory this the applicability of this research is increasing.
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