Quick Facts...
- Leafy spurge (Euphorbia esula L.) is a creeping perennial that reproduces from seed and vegetative root buds.
- It can reduce cattle carrying capacity of rangeland or pastures by 50 to 75 percent.
- Leafy spurge is difficult to control. Its extensive root system has vast nutrient stores that let it recover from control attempts.
- Combine control methods into a system to achieve best results.
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| Figure 1: Number of acres in Colorado infested
with leafy spurge, 2002. |
Leafy spurge (Euphorbia esula L.) is a creeping, herbaceous perennial weed of foreign origin that reproduces from seed and vegetative root buds. It can reduce rangeland cattle carrying capacity by 50 to 75 percent. About half of this loss is from decreased grass production. Cattle won't graze in dense leafy spurge stands and these areas are a 100 percent loss to producers.
A 1990 survey found 44,000 acres in Colorado infested with leafy spurge.
In 2002, the Colorado Department of Agrigculture conducted a follow-up
survey and found more than 73,800 infested acres of leafy spurge.
Leafy spurge is an erect plant that grows 1 to 3 feet tall. Leaves are bluish-green with smooth margins, 0.25 inch to 0.5 inch wide, and 1 inch to 4 inches long.
Umbel flowers are surrounded by heart-shaped, showy, yellow-green bracts. (An umbel looks like the stays of an umbrella if it is held upside down.) Flowers occur in many clusters toward the top of the plant. Seeds are round to oblong, about 1/12 inch long, gray or mottled brown with a dark line on one side.
Leafy spurge contains a white milky latex in all plant parts. Latex distinguishes
leafy spurge from some other weeds (e.g., yellow toadflax), particularly
when plants are in a vegetative growth stage.
Leafy spurge has an extensive root system that is abundant in the top
foot of soil, and it may grow 15 feet deep or more. Roots contain substantial
nutrient reserves that allow the weed to recover from stress, including
control efforts. Many vegetative buds along roots grow into new shoots.
This contributes to its persistence and spread.
Phenology
Leafy spurge shoots originate in early spring from crown tissue just
below the soil surface and from sporadic buds along the root system. Leafy
spurge is very competitive, one of the first plants to emerge each spring,
and uses moisture and nutrients that otherwise would be available for
more desirable vegetation.
Flowering occurs primarily in April and May but may occur through fall. Bracts emerge about two weeks before flowers and give leafy spurge the appearance of flowering. For optimum herbicide application timing, it is important to recognize true flower emergence.
Each flowering shoot produces an average of 140 seeds. Seeds are expelled up to 15 feet when capsules dry. They are viable up to eight years in soil. Water, birds, animals and people aid seed dispersal. Seeds readily float and waterways are good sources for new infestations.
Peak seed germination generally occurs in May. Seedlings quickly acquire the
ability to reproduce vegetatively by developing buds on roots within 10
to 12 days after emergence. Perennial leafy spurge is more difficult to
control than seedlings.
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| Figure 2: Leafy spurge (Euphorbia esula L.) |
Management
Leafy spurge is difficult to manage and can recover from almost any control effort. Therefore, a management scheme that combines control methods over four to five years is recommended. Even after that time, monitor infestations for recurrence and adopt a maintenance program.
Cultural control. Vigorous grass growth is an important aspect of leafy spurge control. Over-grazing stresses grasses and makes them much less competitive with weeds, leafy spurge in particular. Irrigation, where applicable, may favor grass growth and make it more competitive with leafy spurge.
Chemical control. For optimum leafy spurge control, proper
timing of herbicide application is imperative. Research from North Dakota
State University indicates that Tordon 22K (picloram) 2,4-D, Banvel/Vanquish/Clarity
(dicamba) are most effective when applied in spring when true flowers
emerge (not just bracts). Fall application to leafy spurge regrowth also
is good timing for these herbicides.
Roundup (glyphosate) is most effective when applied sequentially (1.0 quart per acre (A) at one month intervals, coupled with fall grass seeding. Make the first application at the beginning of June and a second application one month later. Occasionally, leafy spurge will recover from these Roundup treatments. An application of 2,4-D (2.0 quart/A) in September can control regrowth. Sow perennial grasses in late fall.
Tordon is the most effective herbicide for leafy spurge control. Treat
large, readily accessible areas with 1 quart/A for three to four consecutive
years. More remote areas may be treated with 2 quarts/A for two consecutive
years or once every other year for three years, depending on leafy spurge
recovery after the first treatment. With either treatment, monitor infestations.
Retreat with 1 quart/A of Tordon when shoot control is less than 75 percent.
Tordon may be tank-mixed with 2,4-D to provide adequate control. Apply 1 to 1.5 pints of Tordon with 1 to 1.5 quarts/A of 2,4-D in spring when leafy spurge flowers. When this application is made for three to five consecutive years, leafy spurge shoot control is generally 80 to 90 percent and cattle will feed in the area again.
Banvel/Vanquish/Clarity also is effective against leafy spurge. Apply 2 quarts/A
in spring for three consecutive years. Often control is not very good
in the first year but improves over the next two years. At that time,
a maintenance schedule that uses low rates of Banvel/Vanquish/Clarity
+ 2,4-D (4 to 8 ounces + 0.5 to 1 quart/A), or Tordon + 2,4-D (1 pint
+ 1 quart/A) as needed can be used to keep infestations under control.
Note: Avoid using soil-active herbicides such as Tordon or Vanquish/Clarity
near windbreak plants or other desirable woody vegetation. Plant
injury or death can occur. Also, do not allow any herbicide to drift onto
desirable woody vegetation for the same reasons.
Recently, Plateau (imazapic) was registered to control leafy spurge in noncrop
areas. It can be used safely around trees but may temporarily injure cool-season
perennial grasses. Apply Plateau at 8 or 12 fl. oz/A in fall, followed
by 4 fl. oz/A the following spring at flowering. Add a methylated seed
oil at 2 pints/A to the spray solution. A liquid nitrogen fertilizer solution
may be added to the spray mixture to increase weed control, but it may
increase cool-season perennial grass injury.
Biological control. Sheep or goats can be used to help control
leafy spurge. Research from Montana State University indicates sheep may
consume up to 50 percent of their diet as leafy spurge. Introduce sheep
to leafy spurge in early spring when the weed is succulent. Goats will
consume leafy spurge at almost any time during the growing season.
Rotate pastures to prevent seed production and allow desirable forage plants to regain vigor. If livestock graze leafy spurge after seed formation, hold animals in a corral for at least seven days before moving them to an uninfested area. This reduces viable seed passage. Sheep or goats followed by fall herbicide treatment may be an effective, integrated means to use infested ground and control the weed.
The USDA is examining several insects for leafy spurge control. The Colorado
Department of Agriculture insectary has four flea beetles (Apthona
nigriscutis, black-dot flea beetle; A. cyparissiae, brown-dot
spurge flea beetle; A. czwalinae, black spurge flea beetle; and
A. flava, copper spurge flea beetle) available for release. Their
larvae feed on leafy spurge root hairs and within roots, while adults
feed on foliage. Other insects may become available in the future. Most
likely, a combination of insects will be necessary to adequately control
leafy spurge. Insects would be most advantageous in areas where herbicide
use is difficult or risky.
Recent research completed by Colorado State University showed that six to eight sheep per acre grazing for 10 days in July over a period of five years decreased leafy spurge density about 90 percent. When flea beetles grazed simultaneously in July with eight sheep per acre for 10 days over five years, leafy spurge density was decreased to zero.
Habitat requirements of the flea beetles vary. While all requirements
are not well understood, it is known that A. nigriscutis prefers
open, dry sites and coarse soils low in organic matter. A. cyparissiae
prefers soils higher in moisture than A. nigriscutis, but still
prefers moderately coarse-textured soils such as sandy loams and open
sites. A. flava does well in coarse soils with high water tables
in open and shaded conditions. A. czwalinae prefers moist, clay
soils.
Regardless of the management system used, a combination of methods is essential to return leafy spurge-infested ground to a productive state. The key to control leafy spurge or any creeping perennial is to exhaust the root nutrient stores, causing it to collapse. Persistence is imperative to gain control.
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