This article is a summary of Nebraska Extension Circular EC 174, Noxious Weeds of Nebraska Leafy Spurge and the Extension Circular EC130, EC130, 2021 Guide for Weed, Disease, and Insect Management in Nebraska.
Leafy Spurge, one of Nebraska’s 10 noxious weeds, was first introduced to North America from Europe and was identified in Massachusetts in 1827. In the later 1800s it was likely unknowingly introduced into the north central region of North America through contaminated seed crops imported from Russia and Europe. It was first identified in Nebraska in 1923 in York County.
Biology of Leafy Spurge
Leafy spurge is a creeping, herbaceous perennial weed that reproduces both from seed and vegetative root buds. In Nebraska, shoot emergence frequently starts in early March. Stem elongation and vegetative development increase rapidly as temperatures increase later in the spring. Leafy spurge stems are woody, hairless, erect, pale green and occur in clumps. Leaves are alternate, narrowly linear with smooth margins, about ¼ inch wide and 1 to 2 inches long. Yellow brackets that extend under the flower are most visible from mid-May to June. Seed maturation continues for 30 days after the last flower appears. Flower production and seed development can extend into the fall under favorable growing conditions. A unique characteristic of leafy spurge is the presence of a milky white juice or latex that oozes from cut stems, leaves and roots. Bright yellow brackets and the white milky latex simplify identification.
Leafy spurge is an aggressive competitor with other plants due to its ability to reproduce both by seed and through shoot buds located on the crowns and roots of the plant. Its ability to effectively disperse seed, high seed viability, and rapid seedling development allow for new infestations to establish swiftly. Seed yields can range from 25 to 3,500 pounds per acre, depending on site productivity and density of stands. Seed germination most often occurs in the spring.
Seed from leafy spurge is dispersed in numerous ways. As capsules shrink and split, sufficient force is generated to throw the seed as far as 15 feet. Seeds of leafy spurge can float on water and germinate while floating! This makes spurge especially challenging to control when it is present in watershed areas where water can easily move seed to new locations. Animals such as birds eat and disperse the seeds. Viable leafy spurge seeds have been found to pass through the digestive tract of birds and mammals.
The roots of leafy spurge are composed of main long roots and lateral short roots. Long roots constitute the permanent root system and have the capacity to regenerate roots and shoots. New vertical roots arise on old roots, which allow root penetration to great depths. Individual long roots may live up to four years and reach 15 feet in length. This extensive root system contributes to the plant’s resistance to control measures. While the upper portion of the plant may be killed by herbicide or tillage, root buds below the treated zone can continue to produce new shoots.
Control Methods
The most cost-effective method for leafy spurge control is to identify it early and prevent it from spreading. Biological control can be an effective way to control invasive plants by identifying natural predators to the plant and introducing them to the area where the invasive plant has a foothold. This method of control will not eliminate the plant over time but can be helpful for keeping the plant from spreading significantly. Several insects have been tested, approved and released for biological control of leafy spurge. Different species of beetles that feed on leafy spurge have been successful in controlling leafy spurge in some locations.
Grazing spurge with sheep and goats, especially during early spring growth, can prevent the plant from going to seed. Sheep and goats, once adapted to leafy spurge, can perform quite well, as the forage quality of leafy spurge can be excellent. Mature stands of leafy spurge can be mowed before grazing to improve the palatability of plants. Colorado State University research has shown that numerous consecutive years of grazing by sheep, especially in July during flowering, when combined with flea beetle presence, drastically reduced leafy spurge density. Similar research from North Dakota and Montana has shown reduction to leafy spurge populations in pasture and rangelands when grazed with sheep. Once a population of leafy spurge is established, long-term grazing with sheep and/or goats will likely be needed to limit further invasion. Several studies have shown that leafy spurge re-establishes itself rapidly on range and pasture sites when sheep and goat grazing is removed.
Mechanical control of leafy spurge, utilizing mowing or shredding prior to seed development, will reduce seed production. Multiple years of mowing during flowering and before seed fill will reduce spurge stands by depleting plant energy reserves. However, the root system of leafy spurge is so extensive that total depletion is difficult. Fire has been shown to be no more effective than mowing as a control tool. In some cases, fire can stimulate leafy spurge seed germination. Frequent mowing may also reduce plant vigor of native plants that will compete with leafy spurge on rangeland.
Chemical control with the target of eradication is best focused to small and newly established infestations. Repeated treatment of small infestations can be effective in eliminating the plant. Nebraska Extension Circular EC 130, 2021 Guide for Weed, Disease, and Insect Management in Nebraska, available at your local Extension office and online, has several recommended products that can be effective. Always read and follow label directions before applying herbicides. The optimum time to apply herbicides can vary with the mode of action, with some being more effective in the spring of the year and others being more effective in the fall.
Chemical eradication of leafy spurge often becomes uneconomical as the infestation intensifies. When this occurs, the focus then turns to containment of the leafy spurge to that location by reducing seed production and movement. The use of multiple tools to manage the infestation may be needed, especially on degraded rangelands with a limited number of native plants present to reestablish after removing leafy spurge. An integrated systems approach, using multiple methods to control leafy spurge and to improve rangeland or pasture that has been severely infested is likely the best long-term tactic.