Hemlock, poison (Conium maculatum)

2,4-D or MCPA

Rate 1.5 lb ae/a

Time Apply in seedling to rosette stage of growth.

Remarks Most effective soon after plants emerge. Adding a wetting agent may enhance control.

Caution Do not graze treated area until plants have dried up after spraying.

Site of action Group 4: synthetic auxin

Chemical family Phenoxy acetic 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 broadleaf weeds 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 at 1%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 0.75 lb ae/a

Time Apply to actively growing plants before they begin to bolt.

Remarks Glyphosate is nonselective and will injure or kill grass that might compete with new hemlock seedlings.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

glyphosate (Roundup Pro Concentrate)

Rate Inject 5 ml of a 5% v/v solution into each leaf cane

Time Inject with a hand-held device into one leaf cane per plant, 10 to 12 inches above root crown.

Remarks Mark each plant when injecting it, to avoid re-treating.

Caution Non-Crop use only. Total of all treatments must not exceed 8.5 quarts/a of Roundup Pro Concentrate or 1,600 plants/a.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

metsulfuron (Escort and others)

Rate Escort: 0.6 oz ai/a (1 oz/a)

Time Apply to actively growing plants.

Remarks Use a nonionic surfactant or silicone surfactant. Application sites differ between products; consult labels.

Caution Prevent drift to sensitive plants. Apply only to pasture, rangeland, and non-crop sites.

Site of action Group 2: acetolactate synthase (ALS) inhibitor

Chemical family Sulfonylurea