Spurge, leafy (Euphorbia esula), myrtle spurge (Euphorbia myrsinites), and oblong or eggleaf spurge (Euphorbia oblongata)

Leafy spurge is a creeping perennial that emerges each year from roots that may be exceptionally deep in soil. This weed does not survive under regular cultivation. It becomes serious when it invades pastures and rangeland. Mowing is not effective and is usually impractical. Sheep will graze leafy spurge enough to reduce competition with grass and to allow some production from the rangeland. Any control program, including herbicides, must be long term. Picloram or two or three applications of glyphosate seem to be a good starting point. Establishing a competitive grass and using 2,4-D to prevent seed production and to slow the growth of survivors are essential to return the land to full productivity.

2,4-D LV ester

Rate 1 lb ae/a helps prevent seed formation; 6 lb ae/a helps control leafy spurge infestations.

Time Use lower rates to prevent seed formation in the bud to early bloom stage. Use higher rates in early spring applications.

Remarks When mowing is possible, spray 2,4-D on new regrowth 2 week after mowing. Re-treatments will be necessary.

Caution Avoid drift to sensitive crops.

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 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 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

dicamba (Banvel, Rifle, or Clarity)

Rate 4 to 8 lb ae/a

Time Apply in spring or early summer.

Remarks Dicamba is both soil- and foliar-active. Use on non-cropland only at these application rates. Repeat each year as needed.

Caution Do not graze livestock in treated fields within 30 days of slaughter.

Site of action Group 4: synthetic auxin

Chemical family Benzoic acid

fosamine (Krenite S)

Rate 2 gal product/100 gal water

Time Apply at flowering to actively growing plants. Apply spray to wet.

Remarks Will not kill grasses and can be used next to water. Effectiveness may be reduced if rain falls on the same day.

Caution Non-cropland use only.

Site of action Not well understood

Chemical family Organophosphorus

glyphosate

Rate 0.38 to 0.75 lb ae/a

Time Applications must be split, at 30-day intervals. For the 0.38 lb ae/a (1 pint) rate, apply 1 pint of glyphosate about June 1, July 1, and August 1. For the 0.75 lb ae/a (2 pints) rate, apply 2 pints of glyphosate about June 1 and July 1.

Remarks Three split applications (0.38 lb ae/a each) are somewhat selective, leaving some perennial grasses. These treatments are suggested when water is near the infested area or when a reseeding of grasses is planned. Applications prevent vegetative growth the year of application and will prevent seed production the second year.

Caution Re-treatment is necessary for continued control. Glyphosate is not selective.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

glyphosate + 2,4-D (Landmaster BW)

Rate 54 oz/a Landmaster

Time Late summer or fall.

Remarks Apply in 3 to 10 gal of water.

Caution Glyphosate is not selective; desirable grasses will be killed at this rate.

Site of action (glyphosate) Group 9: inhibits EPSP synthase; (2,4-D) Group 4: synthetic auxin

Chemical family (glyphosate) none generally accepted; (2,4-D) phenoxy acetic acid

imazapic (Plateau)

Rate 0.125 to 0.188 lb ai/a

Time Apply in late summer or fall (mid-August through October) before spurge loses its milky sap due to drought or a killing frost.

Remarks Add 1 quart/a methylated seed oil.

Caution Before using, note crop rotation restrictions.

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

Chemical family Imidazolinone

picloram (Tordon)

Rate 0.5 to 1 lb ae/a. Use higher rates in areas that are difficult to re-treat. Make a series of applications of 0.5 lb ae/a if leafy spurge is near running water or lakes.

Time Apply any time in the growing season. Re-treatments needed for several years to control seedlings.

Remarks Picloram has given excellent control with follow-up treatments. It can persist for 2 years at higher application rates.

Caution Most formulations are restricted-use herbicides. Do not contaminate water. Potatoes, beans, and many other broadleaf crops are sensitive to picloram. Do not use in diversified crop areas.

Site of action Group 4: synthetic auxin

Chemical family Pyridine