University of California

New growth regulator herbicide provides excellent control of yellow starthistle


Joseph M. DiTomaso
Guy B. Kyser
Steve B. Orloff
Stephen F. Enloe
Glenn A. Nader

Authors Affiliations

J.M. DiTomaso is Non-Crop Extension Weed Ecologist, Department of Vegetable Crops, UC Davis; G.B. Kyser is Staff Research Associate, Department of Vegetable Crops, UC Davis; S.B. Orloff is Farm Advisor. Siskiyou County; S.F. Enloe is Graduate Student, Department of Vegetable Crops, UC Davis; G.A. Nader is Farm Advisor, Sutter-Yuba-Butte Counties.

Publication Information

Hilgardia 53(2):12-16. DOI:10.3733/ca.v053n02p12. March 1999.

PDF of full article, Cite this article


Yellow starthistle is the most widespread invasive weed in California. An exotic that invaded California in the Gold Rush days, starthistle was once a minor annoyance but is now out of control. One reason is that few herbicides are registered for use on California rangelands, pastures and wildlands. Of the registered herbicides, the majority are effective only when applied to the foliage of target plants; season-long control of yellow starthistle is not provided because seedlings that emerge after application of the herbicide escape injury. In a comparison of herbicides, the newly registered herbicide clopyralid provided excellent control at low use rates and worked eaually well whether applied to leaves or to soil to control germinating seedlings. In soil, it showed residual activity throughout the season. Complete yellow starthistle control was achieved with applications made from December through April, but treatments in February maximized desirable forage production, particularly grasses. Late-season applications of glyphosate and clopyralid were effective for control of starthistle plants in late rosette and bolting stages.

Further reading

Carrithers VF. Transline herbicide in rangeland and wildlife habitat restoration Proceedings, Calif. Weed Sci Soc. 1998. 50:138-41.

DiTomaso JM, Lanini WT, Thomsen CD, Prather TS, et al. Pest Notes: Yellow starthistle. UC Division of Ag and Nat Resources, No. 7402 1999. p.4.

DiTomaso JM, Orloff SB, Kyser GB, Nader GA. Influence of timing and chemical control on yellow starthistle. Proceedings, Calif. Weed Sci Soc 1998. 50:3.

Lass LW, Callihan RH. Herbicide evaluation for yellow starthistle control. Res Prog Rept. Western Soc Weed Sci 1994. pp.1-42.

Northam FE, Callihan RH. Effects of herbicides on yellow starthistle density and vegetative biomass. Res Prog Rept. Western Soc Weed Sci 1991. pp.43-6.

DiTomaso J, Kyser G, Orloff S, Enloe S, Nader G. 1999. New growth regulator herbicide provides excellent control of yellow starthistle. Hilgardia 53(2):12-16. DOI:10.3733/ca.v053n02p12
Webmaster Email: sjosterman@ucanr.edu