Yellow Starthistle Information

 Mech control
   -hand
   -tillage
   -mowing

 Cultural control
   -grazing
   -burning
   -re-vegetation

 Biocontrol
   -insects
   -biocontrol table
   -plant pathogens

 Chem control
  - risks
    --spray
    --water
    --toxicology
    --herbicide resist
    --effects
   -herbicides
    --preemergence
    --postemergence
    --late season
    --pre- & post-
    --imazapic
    --clopyralid
    --picloram

 Integrated app

 Summary

Management

Picloram

Picloram is the most widely used herbicide to control yellow starthistle in western states other than California, where it is not registered. It acts much like clopyralid, but gives a broader spectrum of control and has much longer soil residual activity. Picloram is applied (usually with a surfactant) at a rate between 0.25 lb and 0.375 lb ae/acre when plants are still in the rosette through bud formation stages (Callihan et al. 1989, Callihan and Lass 1996, Callihan and Schirman 1991, Carrithers et al. 1997, Gaiser et al. 1997, Larson and McInnis 1989b, Lass and Callihan 1995b, Northam and Callihan 1991, Whitson and Costa 1986) [Table A, B, C]. This is typically from late winter to early spring. This treatment can provide effective control for about two to three years (Callihan et al. 1989). Although well developed grasses are not usually injured by labeled use rates, young grass seedlings with less than four leaves may be killed (Sheley et al. 1999b).

Commonly used herbicides for yellow starthistle control (in part from Bussan and Dyer 1999).

Common name	Trade name	Mode of action	Weed Spectrum	Soil residual	Registered in California	Effectiveness on yellow starthistle
2,4-D	Weedar®, Weedone® and many other	Growth regulator	Broadleaf species	No; less than 2 weeks	Yes	Yes; postemergence only from seedling to bolting
Chlorsulfuron	Telar®	Amino acid synthesis inhibitor	Mainly broadleaf species	Yes; at least 2 months	Yes; not in rangelands	Yes; preemergence only
Clopyralid	Transline® Stinger®	Growth regulator	Certain broadleaf families (e.g., Asteraceae, Fabaceae, Umbelliferae, Solanaceae, Polygonaceae)	Yes; full season	Yes	Yes; effective both pre- and postemergence
Dicamba	Banvel® Vanquish®	Growth regulator	Broadleaf species	No; less than 1 month	Yes	Yes; postemergence only from seedling to bolting
Glyphosate	Roundup®	Amino acid synthesis inhibitor	Non-selective	No	Yes	Yes; postemergence only from seedling to early flowering
Imazapyr	Stalker® Arsenal®	Amino acid synthesis inhibitor	Non-selective	Yes; full season	Yes; not in rangelands	Yes; mainly as a preemergence treatment, postemergence control with seedlings or rosettes
Metsulfuron	Escort®	Amino acid synthesis inhibitor	Broadleaf species	Yes; at least 2 months	No	Fair; preemergence only
Picloram	Tordon®	Growth regulator	Broadleaf species, weak on mustards	Yes; up to 3 years	No	Yes; effective both pre- and postemergence; applied fall, winter or spring
Triclopyr	Garlon®, Remedy®	Growth regulator	Broadleaf species	No; less than 1 month	Yes	Yes; postemergence only, good on seedlings, fair on mature plants

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