L.

cheatgrass, downy brome, downy cheat, downy chess, early chess, drooping brome, cheatgrass brome, wild oats, military grass

none known

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CalEPPC Red Alert,CDFA nl

Jim Young

Cheatgrass (Bromus tectorum)
typically is a short grass. Seedlings are bright green with conspicuously
hairy leaves, which suggests the alternate common name, downy brome. At maturity
the foliage and seedheads often become reddish. After maturity the fine herbage
is characterized by a light tan reflectance. The nodding open panicles with
moderately awned seeds (caryopses) are distinctive. Seeds readily penetrate
clothing of passersby.

Cheatgrass is widespread throughout California. It is the dominant annual grass on sagebrush
(Artemisia sp.) rangelands on the Modoc Plateau in northeastern California and along the eastern Sierra Nevada to Owens Valley. It is relatively rare in the annual range
communities of California west of the Sierra Nevada, but widespread throughout the
Great Basin, Snake River Plain, and
the Columbia Plateau. Cheatgrass is a weed of croplands, especially winter wheat
and alfalfa. In wildlands it is most commonly found in sagebrush/bunchgrass
communities, although its distribution extends to higher-elevation juniper,
pinyon-juniper, and pine woodlands.

Cheatgrass grows in many climatic areas.
It is found primarily in locations that receive 6-22 in (15-56 cm) of
precipitation. Cheatgrass will grow in almost any type of soil. Research has
shown that it is most often found on coarse-textured soils and does not grow
well on heavy, dry, or saline soils. Cheatgrass has been found growing on B and
C soil horizons of eroded areas and areas low in nitrogen. It grows in a narrow
range of soil temperatures. Growth starts at just above freezing and stops when
temperatures exceed 60 degrees F (15 degrees C). Litter promotes germination and
establishment of seedlings.

Cheatgrass is native to southern Europe, northern Africa, and southwestern Asia, where it occurs from sea level to 5,000 feet (1,500
m). This grass has been in the shadow of livestock production since ruminants
were first domesticated in southwestern Asia (Young et al. 1972). It has spread to Europe, southern Russia, west central Asia, North America, Japan, South
Africa,
Australia, New
Zealand,
Iceland, and Greenland. It was first identified in the
United
States
in 1861 in New
York and
Pennsylvania and was accidentally introduced to northeastern
California late in the nineteenth century. In 1900 it was found
in Yosemite National Park, and by 1920 it could be found along the Klamath
River, near Yreka (Siskiyou County), Santa Barbara, and Upland in the South
Coast (Robbins 1940). It now occurs throughout the
United
States
(including Hawaii and Alaska), except for portions of
Alabama, Georgia, South Carolina, and Florida. The hairy seed heads are spread by wind, attachment
to animal fur or human clothing, or by small rodents. Contaminated grain seed
probably was the early method of dispersal. Seeds can also be dispersed as a
contaminant in hay and straw or by mud clinging to machinery.

Cheatgrass displaces native vegetation.
It outcompetes the seedlings of native and desirable species for soil moisture.
In a classic paper Robertson and Pearce (1944) determined that cheatgrass closed
communities to the establishment of seedlings of perennial herbaceous species.
Subsequently, it has been determined that cheatgrass also interferes with
seedling establishment of shrubs such as antelope bitterbrush (Purshia
tridentata) and with pine (Pinus sp.) transplants.

åÊ

Cheatgrass changes the frequency, extent,
and timing of wildfires. The early-maturing fine-textured herbage of cheatgrass
increases the chance of ignition and the rate of spread of wildfires. Repeated
wildfires lead to the loss of native shrubs and continued cheatgrass dominance
(Young and Evans 1978, Young et al. 1987). Slow-moving fauna such as
desert tortoises also are sometimes killed in the rapidly moving fires (Lovich,
pers. comm.).

Cheatgrass establishes by seeds only. The plant typically flowers from mid-April through June. It has a tremendous seed production capacity, with a potential in excess of 300 seeds per plant, depending on plant density. Plants as small as one inch (2.5 cm) in height may produce seed. Seed production is so abundant that many seeds do not find safe sites for germination. These seeds can remain dormant in the soil for two to three years. Seeds can withstand extremely high soil temperatures. As a general rule, there are twice as many viable cheatgrass seeds in seedbanks as there are plants established in a given year. The dormancy can be broken by gibberellin treatment or nitrate enhancement of the seedbed. Through the mechanism of acquired seed dormancy cheatgrass enjoys the ecological benefits of continuous germination.

In keeping with its flexible flowering traits, cheatgrass can germinate in fall and act as a winter annual. The primary limit to germination is adequate fall, winter, and/or spring moisture. If fall precipitation is limiting and spring moisture is adequate, germination may be delayed until the following spring. Seeds germinate best in the dark or in diffuse light, and they readily germinate at a wide range of temperatures. They do not need to be in contact with bare soil to germinate, and a litter cover generally will improve germination. However, seeds will germinate more quickly when covered with soil, and seedlings rapidly emerge from the top one inch (2.5 cm) of soil. No emergence occurs from seeds buried four inches (10 cm) below the surface.

(click on photos to view larger image)

Shoot growth occurs in early spring and continues until soil moisture is exhausted. Cheatgrass grows rapidly and may produce dry matter at a rate of 2.9 g/mm2/day. However, growth varies widely from year to year, with practically nothing one year and tons per acre in subsequent years. Extensive root growth can occur during fall and winter. Cheatgrass will produce roots to depths of seven to eight inches (18-20 cm) before sending out far-reaching lateral roots. These lateral roots are one key to survival of this plant. One study showed that cheatgrass has the capability to reduce soil moisture to the permanent wilting point to a depth of twenty-eight inches (70 cm), reducing competition from other species.

Mechanical methods: Mechanical fallows
are effective in controlling cheatgrass and establishing herbaceous perennial
seedlings. The fallow process accumulates moisture and nitrate to aid in
seedling establishment. Tillage in spring after cheatgrass is established is
effective if sufficient moisture remains for perennial seedling establishment.
Mowing has been shown to reduce seed production when the stand is mowed within
one week after flowering. This reduces seed production, but does not eliminate
it because plants that develop later and escape mowing will produce
seed.

Prescribed burning: Burning of pure
cheatgrass stands enhances cheatgrass dominance. This is because wildfires often
occur in late summer or fall, a poor time for perennial plants to reestablish.
Open ground created by fires is readily colonized by annuals such as cheatgrass.
However, burning of mixed shrub-cheatgrass stands generates enough heat to kill
most cheatgrass seeds and offers a one-season window for the establishment of
perennial seedlings. This is why prompt revegetation after wildfires in
sagebrush communities is so important. Because cheatgrass is a cool-season
annual, prescribed fire in late spring might help to control this species,
especially in areas where native warm-season grasses are desired. A prescribed
fire should kill seedlings and further reduce the surface seedbank. Spring
burning of the closely related Japanese brome (Bromus japonicus) showed
that consecutive annual burns reduced brome density and standing crop (Whisenant
and Uresk 1990).

Insects and fungi: No insects or fungi
have been approved by the USDA for use on cheatgrass. Research into the
biological control of cheatgrass is limited. Cheatgrass is often infected with a
head smut fungus (Ustilago bulleta Berk.) that, when severe, may reduce
seed yield. Some research has been conducted on pink snow mold (Fusarium
nivale) as a biological control agent, but information has yet to be
released. In addition to these molds and smuts, over twenty diseases of
cheatgrass have been reported.

Grazing: Grazing management systems that favor
perennial herbaceous species are excellent tools in the suppression of this
pest. This is a good means to avoid the risk of extensive wildfires that cause severe ecological degradation.
Late fall and early spring grazing has been shown to significantly reduce plant
numbers. However, heavy grazing will promote cheatgrass invasion. Encouraging
the reestablishment of native plants improves the effectiveness of grazing as a

Several effective herbicide techniques used in the
past are no longer available. The registrations for these herbicides have either
been lost or not renewed because of cost to the manufacturing companies.
Glyphosate (as Roundupå¨, Rodeoå¨) applications control cheatgrass, but its
effectiveness is limited by the environmental conditions during the cold early
spring when glyphosate should be applied. Several newer herbicides are being
tested for selective control of cheatgrass in perennial broadleaf seedling
stands.

Most of the work on the chemical control
of cheatgrass has focused on infestations in agricultural crops. Chemical
control research in prairies has been primarily limited to atrazine. Herbicides
active on cheatgrass in various crops include diclofop, atrazine, simazine,
amitrole, imazapyr, sulfometuron, paraquat, and glyphosate. Many herbicides are
not specific to cheatgrass or may not be specifically licensed for this
use.