2,4-D or picloram (Tordon) or dicamba (Banvel, Rifle, or Clarity) or 2,4-D + dicamba (Weedmaster) or triclopyr + 2,4-D (Crossbow)
Rate 1 to 2 lb ae/a 2,4-D LV ester or 2,4-D amine; or 0.25 lb ae/a picloram; or 1 lb ae/a dicamba; or 2 quarts/a Weedmaster; or 1.5 to 2 quarts/a Crossbow
Time Apply 2,4-D in spring before any flowers appear; the earlier the application in relation to plant growth, the better the control. Picloram and dicamba can be used at the flowering stage with good results. Fall applications after rains begin seed germination have proven effective also.
Remarks Respraying for more than 1 year is necessary to control late-germinating seeds. Consult labels for grazing restrictions. See also pasture and rangeland section for broadcast spray.
Caution Most picloram formulations are restricted-use herbicides. Avoid drift to sensitive crops. Do not contaminate water with picloram. Potatoes, beans, and many other broadleaf crops are sensitive to picloram. Do not use picloram in diversified cropping areas. Do not graze dairy animals within 2 weeks after application.
Site of action (all) Group 4: synthetic auxin
Chemical family (2,4-D) Phenoxy acetic acid; (picloram and triclopyr) Pyridine; (dicamba) Benzoic acid
aminocyclopyrachlor + chlorsulfuron (Perspective)
Rate 1.8 to 3.2 oz/a aminocyclopyrachlor + 0.7 to 1.3 oz/a chlorsulfuron (4.5 to 8 oz/a of product)
Time Apply to actively growing plants in spring.
Remarks Adjuvants can be used; these include methylated seed oils 0.5 to 1% v/v, nonionic surfactants at 0.25 to 1% v/v, and crop oil concentrates at1% v/v. Can be applied using an invert emulsion rather than water.
Caution Even low rates can kill nontarget tree and shrub species so avoid application within a distance equal to the tree height of the sensitive species. Do not allow spray to drift off target. Can injure several grass species including bromes, as well as basin wildrye.
Site of action (aminocyclopyrachlor) Group 4: Synthetic auxin; (chlorsulfuron) Group 2: ALS inhibitor
Chemical family (aminocyclopyrachlor) Pyrimidine carboxylic acid; (chlorsulfuron) Sulfonylurea
Rate 1 to 1.25 oz ae/a (4 to 5 fl oz/a Milestone)
Time Apply to actively growing plants in the rosette.
Remarks A nonionic surfactant at 1 to 2 quarts per 100 gal of spray enhances control under adverse environmental conditions.
Caution Do not allow drift to desirable vegetation. Many forbs (desirable broadleaf plants) can be seriously injured or killed. Do not exceed 7 fl oz/a Milestone per year.
Site of action Group 4: synthetic auxin
Chemical family Pyridine
metsulfuron (Escort and others)
Rate Escort: 0.45 to 0.6 oz ai/a (0.75 to 1 oz/a)
Time Apply to actively growing plants.
Remarks Use a surfactant to increase effectiveness. Application sites differ among products; consult labels.
Caution Apply only to pasture, rangeland, and non-crop sites.
Site of action Group 2: acetolactate synthase (ALS) inhibitor
Chemical family Sulfonylurea