Leafy spurge [Euphorbia esula L.][EPHES][CDFA list: A][CalEPPC list: A2] Photographs Map of Distribution

Oblong spurge [Euphorbia oblongata Griseb.][Bayer code: none] [CDFA list: B] Photographs Map of Distribution

Toothed spurge or Serrate spurge [Euphorbia serrata L.][EPHSR][CDFA list: A] Photographs Map of Distribution

SYNONYMS:

• leafy spurge:faitours-grass, wolf’s milk, Euphorbia virgata Wald. & Kit., Euphorbia discolor Ledeb., Euphorbia gmelinii Steud., Tithymalus esula Scop., Galarrhoeus esual (L.) Rydb., and many others
• oblong spurge: egg-leaf spurge
• toothed spurge: serrate spurge; saw-toothed spurge.

GENERAL DESCRIPTION:Noxious perennials with milky white latex to 0.8 m tall. Introduced from southwestern Europe.

• leafy spurge: Plants develop extensive creeping root systems and are highly variable. There are many regional biotypes, creating much taxonomic confusion. Dense colonies displace desirable vegetation and reduce the carrying capacity of rangeland. Leafy spurge is particularly troublesome in the Northern Great Plains states. In California it occurs primarily in the northeastern part of the state. The latex of many Euphorbia species is toxic. However, reports on the toxicity of leafy spurge are mixed. In some cases the latex irritates the skin, eyes, and digestive tracts of humans and other animals. Cattle avoid foraging on leafy spurge when possible, but goats and sheep are generally immune to its irritant properties and may develop a preference for it. Mature shoots appear to contain more irritant properties than young shoots. Litter incorporated into soil appears to inhibit the growth of some plants, suggesting allelopathic effects. Several insects have been released as biocontrol agents and are established in certain western states. However, none are established or registered for release in California.
• toothed and oblong spurge: Toxicity is poorly documented, but these species may have irritant properties as well.

SEEDLINGS:leafy spurge: Hypocotyl dull reddish-brown at the soil line, pale green above. Outer root tissues becoming brown and corky at an early stage. Cotyledons linear to elliptic, 2-4 mm wide, 4-19 mm long, becoming leaf-like with age. Upper surface covered with white powdery granules. Lower surface pale and conspicuously veined. Seedling leaves similar in shape to mature leaves except smaller. First leaves opposite. Subsequent leaves alternate but close together so as to appear sub-opposite. Leaf pairs folded or rolled longitudinally in bud, with one leaf enclosing the other. Seedlings develop adventitious buds near the soil line at an early stage. Seedling descriptions for oblong and toothed spurges are unavailable.

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MATURE PLANT:Stems +/- woody at the base. Leaves sessile, glabrous, mostly alternate (some may be opposite or whorled just below the inflorescence branches). Inflorescence bracts opposite, cordate to kidney-shaped, sessile, glabrous, shorter and broader than leaves. Stipules absent.

• leafy spurge: Stems erect, glabrous or hairy. Leaves linear to narrowly oblanceolate, 2-6 cm long, typically about 0.5 cm wide, tips acute or rounded. Margins smooth. Bracts yellow-green.
• oblong spurge: Stems ascending to erect and covered with fine white hairs, especially near the petiole bases and upper stems. Leaves oblong or elliptic, mostly 4-6.5 cm long, tips broadly rounded. Margins minutely toothed (easiest to detect with low magnification).
• toothed spurge: Stems erect, glabrous. Leaves linear to ovate-lanceolate, mostly 2-5 cm long, tips acute to rounded with an abrupt tooth-like tip (mucronate). Margins finely toothed (visible without magnification).

ROOTS and UNDERGROUND STRUCTURES:

• leafy spurge: Develops an extensive system of vigorous, spreading, rhizome-like long horizontal roots, short horizontal feeder roots, and short and long vertical roots. Long horizontal roots and crowns produce many pink scaly buds from which new shoots can develop. Most root buds develop within 30 cm of the soil surface, but a few can develop as deep as 300 cm. Dormant buds on roots and crowns can tolerate temperatures to –13º C (9º F) and to more than –20º C (–4º F) respectively. First year shoots lack woody crowns and are typically more abundant around the perimeter of a clonal population. Vertical roots can reach depths to 9 m (30 ft). Under favorable conditions, root fragments as deep as 2.8 m can produce new shoots for up to 5 years. Long roots become corky and brown with age and can tolerate considerable periods of drought. The root system stores abundant food reserves, enabling roots to produce new shoots for many years under adverse conditions such as continual grazing or mowing.
• oblong spurge: Taproot woody, branched. Stems branch slightly above or below ground. Crown buds develop at the bases of stems and can produce new shoots or roots.
• toothed spurge: Roots are similar to those of oblong spurge.

FLOWERS:Monoecious (male and female flowers separate on same plant). Infloresences umbel-like at the stem tips, with the central inflorescences maturing first (cyme-like). Each infloresence appears to consist of one flower, but is actually a cluster of reduced unisexual flowers (cyathium). A cyathium consists of several staminate (male) flowers, each reduced to 1 stamen, inserted on a glabrous bell-shaped hypanthium (receptacle extension) and one pistillate (female) flower situated above the staminate flowers on a stalk from the center of the hypanthium. Each pistillate flower has 3 styles fused together at the bases and branched at the tips and a 3-chambered ovary. The rim of the hypanthium has 4 flattened glands that lack petal-like appendages. Insect pollinated.

• leafy spurge: June-September. Cyathium 1.5-2.5 mm long. Glands two-horned (crescent-shaped), 1.5-2 mm long. Style branches ½ the style length. Staminate flowers 11-21.
• oblong spurge: Spring/summer. Cyathium 1.5-2 mm long. Glands elliptic, ~ 1 mm long, with outer margins smooth. Style branches less than ½ the style length. Staminate flowers 20-40.
• toothed spurge: Spring/summer. Cyathium 2-4 mm long. Glands oval, ~ 1 mm long, with outer margins smooth or truncate (or sometimes 2-horned). Style branches less than ½ the style length. Staminate flowers 5-20.

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FRUITS and SEEDS:Capsules round, 3-chambered, with 1 seed per chamber. Seeds ovoid to oblong, round in cross-section, 2-3 mm long, and with a yellowish caruncle (small elaisome) near the end of attachment.

• leafy spurge: Capsules 3-5 mm long, smooth to granular. Seeds yellow-brown to gray or mottled, smooth.
• oblong spurge: Capsules 3-4.5 mm long, sparsely covered with minute tubercles. Seeds brown, smooth.
• toothed spurge: Capsules 4-6 mm long, smooth, glabrous. Seeds gray, smooth or minutely pitted.

POSTSENESCENCE CHARACTERISTICS:Leafy spurge shoots die back with the onset of the cold season. Leaves often turn reddish just before dropping. About 42 days of chilling are required to release plants from postsenescent dormancy.

HABITAT: Waste areas, disturbed sites,roadsides, fields, pastures.

leafy spurge: Also, rangeland, alfalfa fields, riparian areas. Plants tolerate sub-tropic to sub-arctic climates, xeric to mesic conditions and flooding for at least 4-5 months if shoots can grow above the water surface. Grows best on coarse-textured soils, although most soil types are tolerated.

DISTRIBUTION:

• leafy spurge: Uncommon. Modoc Plateau (sw Modoc, se Lassen cos.), South Coast (sw Los Angeles Co.). Previous infestations now considered erradicated in Cascade Ranges (ne Siskiyou Co.), eastern Klamath Ranges (cw Siskiyou Co.), southern North Coast Ranges (nw Sonoma Co.); to eastern U.S. To 1400 m (4600 ft).
• oblong spurge: Uncommon. Expanding range. Central Valley, San Francisco Bay region, southern Cascade Range, southern North Coast and North Coast Ranges, South Coast Ranges, northern and central Sierra Nevada foothills. To 200 m (650 ft).
• toothed spurge: Rare. Previous infestations now eradicated occurred in the San Francisco Bay region. To 200 m (650 ft).

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PROPAGATION/PHENOLOGY:Mature capsules of many spurges rupture and forcefully eject seeds some distance from the parent plant.

• leafy spurge: Reproduces by seed and vegetatively from extensively creeping roots. Infestations are usually initiated by seed, but population expansion is mostly vegetative. Seeds mature about 30 days after the female flower appears. Mature capsules eject seeds to 5 m from the parent plant. Some seeds disperse to greater distances with human activities, water, insects (eg., ants), animals, and as a hay or seed contaminent. Some seeds can survive passing through the digestive tracts of sheep and goats, but rarely survive ingestion by mourning doves (Zenaida macroura). Seeds can germinate soon after maturing and can float on water for several days, germinating on the surface. Most seeds germinate in early spring, but germination may occur throughout the growing season under favorable moisture conditions. Optimal germination occurs at temperatures fluctuating between 20-30º C (68-85º F). Light and scarification appear to reduce germination. A cold, moist stratification period followed by warmer temperatures increases germination of some biotypes. Seedling emergence is optimal at depths of 1.5-5 cm, but can occur from depths to ~ 15 cm. Under field conditions, some seeds can remain viable for at least 8 years. Most seedlings do not flower the first season. Individual shoots typically produce ~ 10-50 capsules. Flower production and shoot survival decrease with increasing shade.
• oblong and toothed spurge: The biology of these species is poorly documented.

MANAGEMENT FAVORING/DISCOURAGING SURVIVAL:Wearing gloves while handling plants can prevent skin irritation from the sap.

leafy spurge: Mowing, burning, and grazing do not significantly affect roots and typically stimulate the production of new shoots from root buds. Continuous grazing by sheep or goats can reduce the soil seed bank by preventing flower production, but roots can continue to produce shoots for many years (>8 years). Livestock, especially sheep and goats, foraging on plants in fruit should be quarantined for 5-6 days before transporting to uninfested areas to prevent the introduction of seed. Cultivation or discing can spread infestations by transporting root fragments and seeds.

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SIMILAR SPECIES:There are many weedy spurge species, several of which appear similar. Refer to the tables Spurge: vegetative characteristics and Spurge: reproductive characteristics for comparison. The following species are most likely to be confused with leafy, oblong, and toothed spurges.

sun spurge, wartweed [Euphorbia helioscopia L.][EPHHE]: Annual to 0.5 m tall. Flowers March-August. Disturbed sites, waste areas. Northern and central North Coast, northwestern and central-western North Coast Ranges, San Francisco Bay region, South Coast. To 200 m (650 ft). Introduced from Europe.

caper spurge, gopher plant [Euphorbia lathyris L.][Cal EPPC list: need more information]: Potentially noxious annual or biennial with opposite leaves, to 1 m tall. Flowers most of year. Disturbed sites, waste areas, roadsides, coastal scrub, marshes, dunes. North, Central, and South Coasts, Central Valley. To 200 m (650 ft). Introduced from Europe.

Geraldton carnationweed [Euphorbia terracina L.]: Potentially noxious perennial or biennial, to 0.5 m tall. Often forms dense patches. Flowers March-(August). Disturbed areas, including disturbed grasslands, coastal bluffs, dunes, salt marsh, riparian areas, oak woodlands. Uncommon. South Coast (Los Angeles Co.). Recently introduced from southern Europe and the Mediterranean.

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CONTROL METHODS:

Prevention: Leafy spurge is an extremely noxious weed found throughout the Western United States. It is toxic when eaten by cattle and horses and may irritate the skin and eyes of humans who come in contact with its milky latex. It reduces forage quality and subsequent livestock carrying capacity. Leafy spurge is a very aggressive, deeply rooted perennial that effectively competes with native plants. Established stands are very difficult to control. It is classified as a CDFA class "A" noxious weed and should be aggressively managed to prevent its spread. There is considerable information regarding the control of leafy spurge, but little is known about oblong or serrate spurge. Serrate spurge is also a class A species and oblong spurge is a class B species. Regardless, they should also be managed to prevent spread from known infestations.
Leafy spurge may be spread by humans, animals, equipment, and through contaminated hay. It rapidly colonizes disturbed areas in pastures, rangelends, and roadsides. It may also persist along waterways and riparian areas, and is often transported by moving water. Cattle will generally avoid leafy spurge and subsequently overgraze more desirable neighboring plants. This type of selection allows leafy spurge to rapidly establish large dense stands. Therefore, avoid overgrazing and excessive disturbance in pastures and rangelands, and reduce cattle stocking rates in areas of known infestations.

Mechanical: Leafy spurge will not usually persist in agricultural fields that use conventional tillage practices. However, it can be a problem in fields where reduced or no-tillage systems are used. Herbicide rates required for leafy spurge control will almost always exceed rates allowed in cropping systems. Therefore, it may be necessary to implement a cultivation program to reduce infestations. Two post-harvest cultivations in the fall to a depth of at least four inches will help reduce infestations. This should be conducted for two to three years. It is very important to clean tillage equipment after cultivating fields infested with leafy spurge, as plant regeneration can occur from very small root segments.
Hoeing, grubbing, or hand pulling leafy spurge is a very difficult task, but may be used for small patches. These control methods will need to be repeated several times over the growing season, due to regeneration of new shoots from root buds. Long term control may require several years of diligence when using these methods. Gloves are recommended when handling leafy spurge due to the irritating effects of the latex. Avoid rubbing your eyes or face after handling leafy spurge, and always wash with a detergent and warm water.
Mowing is generally not effective for reducing leafy spurge infestations. However, mowing every 2-4 weeks can reduce seed production. Mowing may result in more uniform spurge regrowth, which is more conducive to uniform herbicide applications. However, this does not guarantee improved control.

Fire: Fire has not generally been successful for controlling leafy spurge, due to rapid regeneration. Fire may be beneficial in other ways, by removing litter and dead stems. Fire may also stimulate bunchgrass growth, which may improve its competitive ability with leafy spurge.

Biological: There are no current biocontrol programs for oblong spurge or serrate spurge. However, there are several insects approved for use as leafy spurge biocontrol agents in the United States. To date, none are known to have established in California. Five flea beatles (Aphthona spp.) have been established in many areas across the Great Plains and Pacific Northwest. They are destructive in a two-fold manner. The larvae feed on the root hairs and roots, and the adults feed on the stems, leaves, and flowers. Flea beetle establishment may take three to five years, and success varies with differing environmental conditions. Once established, flea beetles may significantly reduce spurge populations. However, new shoots will emerge from dormant root buds on undamaged roots.
Three moths (Chamaesphecia spp.) are being tested but are not currently available for distribution. They are destructive in the larval stage by feeding in the roots. Another moth (Hyles euphorbiae) has been established in certain areas, but is not effective when used alone. These and other insects may eventually provide long term leafy spurge management, but should not be used alone where eradication is the objective.

Table 1. Insect species introduced into the United States for the control of leafy spurge

Grazing: Although leafy spurge is toxic to cattle and horses, goats and sheep are tolerant and have been successfully used in control programs. A grazing program should be implemented in the spring when leafy spurge emerges. Researchers at North Dakota State University recommend sheep stocking rates of 3-6 head per acre of leafy spurge infested land per month, or 12-16 Angora goats per acre of leafy spurge per month. These animals will not eradicate leafy spurge, but will allow grasses to more effectively compete and become established. It is extremely important to place animals in a holding pen for 3-5 days before moving to a new area. This will prevent viable seed from being dispersed to new areas through the animals.
A dual grazing-herbicide strategy that allows for leafy spurge regrowth in the fall followed by a herbicide application has been proven more effective than either strategy alone. Interactions between biocontrol insects, herbicides and grazing are not fully understood. However, where flea beetles are established, herbicide applications can affect flea beetle populations by removing their food source. The gall midge (Spurgia esulae) has been shown to be compatible with herbicide applications, as long as a few patches are left untreated to sustain the gall midge population.

Competitive species: There is little information regarding establishment of competitive native species on leafy spurge infested land in California. Research from North Dakota State University indicated that Russian wildrye, pubescent wheatgrass, smooth brome, western wheatgrass, and Dahurian wildrye, were competitive with leafy spurge. These may or may not be desirable replacements, according to the goals and objectives of the land manager.

Chemical: Leafy spurge is very resilient to most herbicides due to regeneration from dormant root buds. Its extensive root system maintains a large pool of carbohydrates that allow for rapid shoot regeneration. One herbicide application will not provide long term control, and retreatment will be necessary for several years. Application timing is critical for herbicide effectiveness. Dicamba (4-8 lb ae/A) and 2,4-D (1-6 lb ae/A) are most effective when leafy spurge plants are flowering in early summer, or during he fall when regrowth has occurred. The lower rates will prevent seed production but will not provide long term control. Glyphosate (0.38-0.75 lb ae/A) is more effective after plants have begun filling seed. However, this will allow for some seed production and may not be the best strategy for an eradication program. Another strategy is to apply glyphosate in split applications over the summer in June, July, and August. This will control emerged plants and prevent seed production. The most effective herbicide for leafy spurge control is picloram at 0.5-2 lb ae/A. However, picloram is not labeled for use in California.
These rates of dicamba and 2,4-D will initially have a severe impact on desirable forbs and legumes, and yearly repeat herbicide applications may substantially reduce their recovery. Glyphosate is nonselective and will injure or kill other vegetation it contacts. Where infestations occur along water, an aquatic formulation of glyphosate (Rodeo) or 2,4-D can be used to prevent seed production. In wooded areas, dicamba may not be used and either glyphosate or 2,4-D amine formulation can be applied. It is very important to minimize drift in these areas, as significant injury to trees and shrubs may occur. It is also recommended that herbicide applications extend 3-5 m beyond patch edges due to the creeping nature of the roots. Herbicide use for managing leafy spurge is very costly and must be integrated with other strategies for long term success. Any control efforts not maintained on a yearly basis will result in complete and rapid reinfestation.

Integrated management: The best defense against leafy spurge is preventing infestation. Rapid identification and response may prevent leafy spurge from becoming a problem. Small patches should be aggressively controlled and monitored often for regrowth. Once infestations become larger, control is very difficult and costly. No single control measure will eliminate leafy spurge. However, integrative methods that utilize a number of techniques have been shown to successfully control infestations. There is also an interactive compact disc entitled "Purge Spurge: Leafy Spurge Database" which was developed by the United States Department of Agriculture/Agricultural Research Service, in conjunction with Montana State University. This is a comprehensive source of information on the biology and control of leafy spurge and is very easy to use. More information is available at the web site: http://www.sidney.ars.usda.gov

References
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