Invasive Plants of California's Wildland

Halogeton is an annual herbaceous plant, typically six to twelve inches tall, with short, fleshy, sausage-like leaves less than half an inch long. One of its most distinctive features is the conspicuous, soft, slender spine at the bluntly rounded tip of each leaf. Plants are often bluish green in spring and early summer, turning yellow, salmon, pink, purplish, or even reddish by late summer or early fall. Stems often turn pink or red while leaves are still blue-green. Plants can resemble Russian thistle in early stages of growth, but are distinguished easily by the unique leaf tips and the presence of tiny, cotton-like hairs in the leaf axils.

In 1980 halogeton was reported in Inyo, Kern, Lassen, Los Angeles, Modoc, Mono, and Nevada counties in California. Today it can be found throughout southern California and in all counties bordering Nevada. It has also been reported from Siskiyou and San Diego counties. Halogeton is widely distributed over millions of acres throughout at least eleven western states from about 2,500 to 7,000 feet elevation. It is highly suited to the alkaline and saline soils of the region’s semi-arid high-desert environments, but it also may be found on heavy clays, clay loams, sandy loams, and loamy sands. The abundance of halogeton depends upon year-to-year precipitation, so outbreaks may appear sporadically. Annual precipitation at most halogeton sites is from five to thirteen inches (127-330 mm) (Cooke 1965).

Halogeton is found mainly on disturbed arid sites in saltgrass, salt desert shrub, mixed desert shrub, or pinyon-juniper plant communities. Annual weeds typically associated with halogeton include cheat grass (Bromus tectorum) and Russian thistle (Salsola tragus ). It is especially common along roadsides, on the edges of alkaline flats, in livestock bedding or feeding areas, in abandoned dryland farms and townsites, and around desert watering sites (Pemberton 1986, Bellue 1951).

Halogeton is native to Eurasia or Siberia and was introduced into the United States in northern Nevada in the early 1930s, possibly for use in grazing experiments. The first herbarium specimen was collected in 1934 in Nevada. It spread quickly into desert lands throughout Nevada, Utah, California, and adjacent states (Cook and Stoddart 1953). Halogeton can be dispersed by wind, water, animals, and human activity. Local dispersal by wind is aided by winged bracts on the black seeds. Entire plants can become tumbleweeds, driven by wind or catching on the undercarriage of vehicles, distributing seeds for great distances. Whirlwinds or dust-devils can transport dry stems with seeds up to two miles. Animals can spread large amounts of seed great distances because the seeds are resistant to digestion (Whitson et al. 1991, Dayton 1951, Stoddart et al. 1951). Halogeton seeds are rapidly spread along roads by equipment, especially road graders (Cronin 1965).

Halogeton is not an extremely competitive plant, but it can quickly invade disturbed or overgrazed sites, and it can prevent reestablishment of desirable species. It is poisonous to livestock. Sheep are especially prone to poisoning, although cattle also can be affected (James et al. 1980). Leaves and stems are rich in a toxic substance called sodium oxalate. Halogeton is readily consumed by hungry or thirsty livestock and is responsible for thousands of livestock deaths. Signs of poisoning include depression, weakness, reluctance to move, rapid and shallow respiration, drooling, recumbency, coma, and death within two hours to several days after ingestion (Bohmont et al. 1955). The best defense against poisoning is to keep livestock away from infested sites, especially after drinking or following a rain or snow storm (Burge 1950, Cook and Stoddart 1953).

Reproduction of halogeton is exclusively by seed. Flowering typically begins in June. Fruiting and seed production are generally from July through October. Halogeton can produce seventy-five seeds per inch (35 seeds/cm) of stem, or 200 to 400 pounds of seeds per acre (222-449 kg/ha). More than 100,000 seeds can be produced on a single large plant. Two types of seeds are produced, which is important to the plant’s spread and persistence. Black seeds germinate during the first growing season after production; brown seeds can remain viable but dormant in the soil for ten years or more (Cronin and Williams 1966).

Halogeton takes advantage of infrequent desert precipitation by emerging quickly when soil moisture becomes available from February to mid-August. Plants grow rapidly and produce an abundant seed crop before frost ends the growing season in fall. Halogeton usually establishes first in disturbed sites, such as along road shoulders or livestock trails and bedding areas (Erickson et al. 1951).

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If eradication of small, isolated patches of halogeton is the goal, it will be necessary to monitor infestations at least once or twice each year to make sure no seedlings survive to produce seed. This will have to be done for at least ten consecutive years, because halogeton seeds can remain dormant but viable in the soil for that length of time. Controlling extensive infestations will require elimination or reduction of the disturbance that allowed halogeton to invade and simultaneous reestablishment of competitive perennial grass, forb, and/or brush species (Fenley 1952).

Manual/mechanical methods: Because halogeton is a simple shallow-rooted annual, it can be controlled effectively by tillage or pulling. Plants are easiest to control as seedlings or in early vegetative growth. Plants not controlled until after flowering begins may contain seeds and should be removed and destroyed to prevent reseeding. Periodic mowing close to the soil surface can significantly reduce but not completely prevent seed production. Surviving branches below the reach of mower blades will continue to produce viable seeds.

Prescribed burning: Halogeton is not controlled effectively by burning, and it is one of the first plants to reestablish following wildfire on infested rangeland.

Insects and fungi: A stem-boring moth, Coleophora parthenica , was introduced by the USDA into the United States for possible control of halogeton, but it failed to establish. Other potential biological control agents have been identified in Central Asia, but they have not yet been developed and tested.

Grazing is not a control option because of the toxicity of the plant.

Glyphosate (as Roundup®; 2 percent solution) in a spot treatment on small infestations will kill emerged halogeton plants if applied before the bloom stage. Repeat treatments will be necessary to control any flushes emerging later in the season. Herbicides containing the active ingredient metsulfuron (in Escort® or Ally®) effectively control more extensive infestations of halogeton in pastures and rangeland without causing injury to desirable grasses. Colorado State University studies comparing various rates of metsulfuron, dicamba (as Banvel®), and picloram (as Tordon®) reported good initial control from each herbicide when applied in spring to small, one- to three-inch (2.5-7.5 cm) tall halogeton plants. However, effects of many treatments were temporary. Five months after application, control from metsulfuron remained good to excellent (73-94 percent). However, dicamba provided poor to good control (48-78 percent), and picloram treatments were rated as poor (19-53 percent control) (Sebastian and Beck 1993).