Cheatgrass MC

Species Management and Control Information

Cheatgrass (Drooping brome-grass)
Bromus tectorum L.

SOURCE: The following information is taken from a number of sources and those sources are identified at the beginning of the referenced information. The intent of this resource is to provide the user with as much of the information that exists for management and control of this species as is practical. It is important to note that new and improved methods are added regularly which will require you to visit the websites provided for updates on this information. Bibliographies and resources referenced by these sources are not included here, but are included at the websites from which this information was extracted.

READ THIS FIRST!

Before administering any of the following management and control options, it is imperative that you are familiar with the background information provided under the General Management and Control Section.

For additional, and potentially more current, information on management and control of this species, use the Mid-Atlantic Exotic Pest Plant Council (MA-EPPC) listserve or any of the other listserves identified in the Resource - Listserve section of this tutorial. You will find directions for subscribing to the list serve there. The MA-EPPC listserve has an archives feature that saves past discussions (beginning in 1999) about specific species control. These messages are at: http://groups.yahoo.com/group/ma-eppc/messages.

GENERAL MANAGEMENT CONSIDERATIONS:

Montana State University - Weed Science - Bromus tectorum - http://weeds.montana.edu/crop/brome.htm - Authors: Meghan Trainor, Alvin J. Bussan - September 19, 2001

Prevention
| Despite successful efforts to control downy brome in croplands -- infested rangelands, pastures, roadsides, and waste areas throughout Montana provide a continuing source of downy brome seed for reinvasion of winter wheat crops. Seed spread is mainly through contaminated grain, hay, straw, manure and farm machinery. The long awn attached to the seed helps it stick to animal fur, as well.

To prevent initial infestation in cultivated land, ensure that any seed purchased is certified free of downy brome and thoroughly clean equipment, especially swathers and combines. Four main reasons are cited as to why downy brome has become more of a major problem in cultivated land.

1. Farmers are re-cropping more, thereby not allowing for the opportunity to break up the downy brome life cycle.
2. The shorter wheat varieties used today allow more light to penetrate the crop canopy, making downy brome more competitive.
3. More fertilizer is used each year giving downy brome a competitive edge.
4. Farmers rarely use the mold-board plow and are instead using variations of either stubble/mulch tillage or no tillage at all. The chisel plow doesn't invert soil, and as a result, downy brome seed is no longer buried deeply. In no-till farming, downy brome seed remains on the soil surface which is the preferred environment of this plant since it is a surface germinator. It thrives under no-till production. Shallow burial, or surface germination, is the ideal germination environment for downy brome (Wright and Fay 1995).

Cultural Control
Cropland Weed Specialist, A.J. Bussan at MSU in Bozeman, says the first key to successful control of downy brome it to select appropriate fields. Crop rotation is the principal management strategy for downy brome. For example, downy brome populations increased from 2 up to 60 plants per ft2 after 3 years of continuous winter wheat in research trials. In contrast, winter wheat - fallow or winter wheat - canola rotations maintained downy brome populations below 10 plants ft2 in the same study. As a result, a number of Montana growers have adopted a 3 or 4 year rotation that alternates spring crops with winter wheat and fallow. In selecting fields for planting winter wheat, growers should select fields where the downy brome has been effectively cleaned up by crop rotation.

Another approach involves timely summer fallow tillage. The major cause of the downy brome problem is annual seed production. Timely summer fallow tillage will break this cycle. Downy brome matures quickly in the spring (hence the weed's other common name Junegrass). Therefore, summer fallow tillage must occur early enough to prevent seed production. If seed heads emerge from a downy brome plant before tillage or after tillage, viable seed will be produced and must be dealt with in the fall prior to seeding winter wheat. Pre-plant control is another effective strategy. The most common technique used by Montana farmers to control downy brome is to delay winter wheat seeding in the fall until rains occur. This stimulates germination of downy brome seed which is easily controlled during winter wheat seedbed preparation. Bussan suggests preparing a firm seedbed 2 weeks prior to planting. The tillage and mixing of wet and dry soil can stimulate downy brome seed to germinate and emerge. The emerged downy brome can be managed by additional tillage or herbicide application prior to planting. Popular herbicides for pre-plant management include Roundup or Gramoxone Extra. Both products can be applied after planting, but before crop emergence, as well. Roundup and Gramoxone Extra should be applied with ammonium sulfate. Be sure to follow the label for proper rates.

For growers with limited or no-till cropping systems, stale seed bed techniques may not fit. However, using a Phoenix or spring-toothed harrow prior to planting may stimulate emergence, in particular if rain occurs prior to planting. In addition, growers could use stale seedbed techniques on field edges or in problem areas where downy brome is likely to occur to prevent its spread across fields.

Narrow row spacing of winter wheat reduces the competitive ability of downy brome. However, this is not a feasible practice in the dryer areas of Montana due to increased competition among wheat plants for moisture.

For those farmers who anticipate a downy brome problem, increasing the seeding rate of winter wheat can be an effective technique. Increasing the seeding rate of winter wheat creates more competition for the downy brome plants.

Downy brome evolved in a rangeland situation and is therefore adapted to that type of environment. Thus, the seed germinates easily on the soil surface, but less effectively when buried. Researchers in Washington report that firmer seedbeds allowed fewer downy brome seedlings to emerge.

Since downy brome grows along roadsides, it serves as a source of seed which can infest adjacent cultivated land. The summer fallowing pattern of cultivated land can eliminate much of the downy brome seed that's produced along the borders of fields.

MANUAL AND MECHANICAL CONTROL:

Montana State University - Weed Science - Bromus tectorum - http://weeds.montana.edu/crop/brome.htm - Authors: Meghan Trainor, Alvin J. Bussan - September 19, 2001

Neither mowing nor burning are effective controls to prevent seed set. Seed will continue to mature on cut-off plants. One option is mowing and removal of plants from the field. Burning is not effective, as many of the seeds drop to the ground before the heat can kill them.

As discussed above early spring tillage of fallow ground, tillage prior to planting spring-season crops, and tillage operations that bury downy brome seeds (mold-board plowing) are effective mechanical methods.

The Nature Conservancy - Invasive Species Initiative - Species Management Summary (ESA or Element Stewardship Abstract): Bromus tectorum - http://tncweeds.ucdavis.edu/esadocs/bromtect.html - Authors: Alan T. Carpenter and Thomas A. Murray - 1999.

CONTROL WITH CUTTING: Cutting is not a recommended control method for cheatgrass. Plants that are cut before seed ripening will regenerate new culms and produce seeds at the cut height. Plants that are cut after seed ripening will die, but by this point the seeds are already viable. For more information, see Lawrence Memorial Grassland Experiment in the Management Programs Section.

CONTROL WITH GRAZING, DREDGING, AND DRAINING: Bromus tectorum is considered to be valuable forage in some ranching operations (Emmerich et al. 1993). However, grazing is not a recommended method of control for cheatgrass. If the plants are grazed in the spring, they will regenerate new culms and produce seeds. When grazed in the summer or fall the plants will not regrow, but by then viable seeds have already been produced. Also, the long awns of the seeds on the mature plants may damage the mouths and intestinal tracts of the livestock.

There are no references to indicate that dredging or draining have been tested, or would be an adequate control method for Bromus tectorum. Cheatgrass does not usually grow in sites that could be dredged or drained.

CONTROL WITH MANIPULATION OF WATER LEVEL AND SALINITY: There are no references to indicate this has been tested, or would be an adequate control method for Bromus tectorum.

CONTROL WITH MOWING, DISKING, AND PULLING: Mowing is not usually an effective control of Bromus tectorum (Whitson et al. 1997). Although cheatgrass plants will die if they are mowed after ripening, by then the seeds are already viable. When mowed at an earlier growth stage, the plants can regenerate new culms and produce viable seeds. Therefore, mowing once a year does not prevent stands from producing viable seeds (Whitson et al. 1997).

In one study, repeated mowing (every three weeks) during the spring and summer was as effective at controlling cheatgrass seed production as an application of glyphosate (Ponzetti 1997). However, this method was very labor-intensive and a cost/benefit analysis should be conducted before any choice is made.

Hand-pulling cheatgrass plants in small infestations before seed set would effectively eliminate current seed production, but may not eliminate the infestation. The large seed bank commonly associated with cheatgrass infestations will allow plants to re-establish for several years without noticeable reductions in plant density. Hence, any pulling program must be conducted for several years, or until the seed bank has been exhausted. Also, seeds that blow into the cleared areas from adjacent uncleared areas may negate the effects of pulling. When pulling, an effort should be made to extract as much of the root as possible so that the plant can not simply regrow and produce new seeds.

PRESCRIBED FIRE:

Bromus tectorum is a highly flammable species due to its complete summer drying, its fine structure, and its tendency to accumulate litter (5). A fire will reduce the plants to ash, but fire intensity may not be great enough to consume the litter layer, and seeds in the soil will probably survive (5). The amount of litter or ash left on a site is a good indicator of the amount of cheatgrass seed still surviving (5).

Wendtland (1993) studied the effects of spring, summer, and fall burns on mixed-grass prairie in western Nebraska that had been tilled in the distant past and had subsequently reverted to prairie ("go-back" lands). The study sites had abundant cheatgrass. He found that both summer and fall burns were effective at controlling cheatgrass without severely damaging most native species plants. However, he recommended fall burns because they were much easier to control than summer burns. Interestingly, blue grama (Bouteloua gracilis), which is often the dominant plant over vast areas of short-grass prairie, was damaged significantly more by burning than other native plant species.

In Colorado, burning is usually conducted in June after the plant has dried, but before the seeds have dropped (Beck pers. comm.). However, some seeds will survive and if a burn is not followed by reseeding cheatgrass will recover to pretreatment proportions within 3 to 4 years (Beck pers. comm.). Reseeding should be done in late fall (a dormant seeding) (Beck pers. comm.).

Cheatgrass fires may reduce the cover of valuable perennial species e.g., shrubs like sagebrush and grasses like bluebunch wheatgrass, that are not adapted to frequent fires (5). Additionally, areas that have been burned become susceptible to erosion until they green up again.

Cheatgrass fires can burn very rapidly and can be very dangerous. Firefighters have reported cheatgrass fires that traveled between 20-40 mph, over-running firefighters and equipment (Devine 1998). Controlled cheatgrass burns should always be conducted by trained individuals.

BIOCONTROL:

Montana State University - Weed Science - Bromus tectorum - http://weeds.montana.edu/crop/brome.htm - Authors: Meghan Trainor, Alvin J. Bussan - September 19, 2001

The studies on potential biological controls of downy brome have mainly focused on downy brome in a rangeland environment. One such study looked at potential biological control of downy brome with crown and root rot fungi. The researchers suggested that crown rot might be a potential biological control on downy brome in the arid western U.S. because it is adapted to dry soils and has low virulence on desirable grasses, such as wheatgrass (Grey et al. 1995). Thus, crown rot causes greatest damage on moisture-stressed plants and results in susceptible disease reactions on downy brome.

No biological control agents are available for use against cheatgrass at present. The biological control of weeds is based on the premise that insect feeding stresses or kills plants or reduces seed output and eventually causes a reduction in weed density (Berube and Myers 1982). Biological agents have never been known to completely eliminate the host species, but can significantly reduce their abundance. In fact, complete elimination would be self-defeating to the control agent. However, if different stresses on plants are cumulative, biological controls which lower the competitive ability of weeds should enhance the effectiveness of other control methods.

In laboratory and small-scale field tests, phytotoxins produced by the naturally occurring rhizobacteria, Pseudomonas fluorescens (strain D7), and Pseudomonas syringae (strain 3366) adversely affected cheatgrass at several growth stages (Gealy et al. 1996, Gealy et al. 1995). These bacteria produce plant suppressive compounds (PSC's) that selectively inhibit the germination and early root growth of cheatgrass, and thus shift the competitive advantage back to perennial grasses (Ogg et al. 1991). The active compound produced by these bacteria appears to be a phenazine-1-carboxylic acid (Gealy et al. 1996). When purified from strain 3366 and applied at a rate of 5.7 mg/L, the acid inhibited downy brome root growth by 99% (Gealy et al. 1996).

The phytotoxins produced by strain D7 and strain 3366 inhibit lipid synthesis and disrupt membrane integrity (Gealy et al. 1996). These two effects can stop cheatgrass seedling growth within several hours after exposure (Gealy et al. 1996). Further tests indicated that cheatgrass root growth is about 200 times more sensitive to D7 than shoot growth (Gealy et al. 1996). Gealy et al. (1996) determined that older seedlings were inhibited several orders of magnitude less than very young seedlings. The greatest suppression of cheatgrass occurred in cool (10/10 or 18/13ºC) (50/50 or 64.4/55.4ºF) or moist conditions (Johnson et al. 1993). Since cheatgrass seeds usually germinate and establish in the fall, the application of bacterium would need to be timed to coordinate with seedling emergence.

Neither of these two rhizobacteria are currently approved as biological controls for cheatgrass. The focus of the research on them has been to develop a biological control for cheatgrass in winter wheat crops and the effects of these rhizobacteria on desirable plants in noncrop applications has not been determined. Additional research may be able to determine if these agents can provide effective control of cheatgrass on the ground in noncrop situations and natural areas.

CHEMICAL CONTROL*:

Montana State University - Weed Science - Bromus tectorum - http://weeds.montana.edu/crop/brome.htm - Authors: Meghan Trainor, Alvin J. Bussan - September 19, 2001

Herbicide programs have been developed for downy brome control in alfalfa, perennial grasses grown for seeds, and for some rangeland plants. In winter wheat, however, chemical control is difficult due to the species having similar growth habits and susceptibility to herbicides.

The herbicides that control downy brome include atrazine, bromacil, cyanazine, chloropropham, diclofop, glyphosate, metribuzin, paraquat (with or without selected triazines), pronamide, propham, simazine, terbacil, and trifluralin (Wicks 1984; Pepper 1984; Swan and Whitesides 1988).

There are several types of herbicides that can be used alone or combined to provide effective control of Bromus tectorum. For relatively small infestations, a backpack sprayer is recommended to minimize the danger to non-target plants. However, infestations are often so large that a four-wheeler, tractor, or truck fitted with a sprayer is necessary. The following herbicides are divided into two groups, spring applied and fall applied.

Spring Applied Herbicides: In most cases, applications should be made in early spring when non-target species are dormant to ensure selective control. Cheatgrass was reported to be controlled best when the plants were 10 cm (3.9 in) high or less and growing vigorously at the time of application (Wiese et al. 1995).

Quizalofop: Trade Name: Assure II®: Whitson et al. (1988) reported that quizalofop applied in mid-April at a rate of 0.5 lb./acre controlled 100% of the cheatgrass in the study. However, the herbicide suppressed seed head production of perennial grasses (Whitson et al. 1988). In another study, quizalofop at 0.02 lb./acre provided greater than 95% control of cheatgrass. No mention was made of damage to perennial grasses (Wiese et al. 1995).

Quizalofop is a grass meristem destroyer, and is usually used to remove grass species from any non-grass crop (Ross and Childs 1996). All grass meristem destroyers should be used post-emergence on seedling grasses before the seed head is detectable in the top leaf sheath (boot stage) (Ross and Childs 1996). Once applied, leaves yellow, redden, and sometimes wilt (Ross and Childs 1996). Quazalofop does not damage most broadleaf species and is registered in the United States for noncrop use outside California (DuPont, 1999a).

Fluazifop-p-butyl: Trade names: Fusilade® 2000, Fusilade® DX: Fluazifop-p-butyl is another postemergence herbicide that attacks the meristematic tissue of annual and perennial grass species (Ross and Childs 1996). Fluazifop-p-butyl is actively taken up and translocated throughout the plant (7). It accumulates in the actively growing regions and interferes with the plant cell's ability to produce energy (7). Fluazifop-p-butyl does not kill broadleaved plants, and at sublethal rates will suppress seed head development in cheatgrass (Ahrens 1994). At very low rates, fluazifop-p-butyl retards grass growth (Ahrens 1994). However, if considering using low rates of fluazifop-p-butyl against cheatgrass, the herbicide's effects on desireable non-target grass species should be determined on a site by site basis.

The application rate in noncrop situations is generally 16-24 oz/acre (1-1.5 lb./acre). Like quizalofop, fluazifop-p-butyl should be applied early post-emergence, before the seed head is detectable in the top leaf sheath (Ross and Childs 1996). Fluazifop-p-butyl is not registered for use on Bromus tectorum in California.

Sethoxydim: Trade names: Poast®, Poast Plus®: Sethoxydim is a postemergence herbicide used to control annual and perennial grass species (8). Like quizalofop and fluazifop it does not damage most broadleaved species (forbs and woody plants). Sethoxydim is commonly used to control grass weeds in broad-leaved vegetable, fruit, field and ornamental crops (8). Sethoxydim has been used in noncrop situations as well. It is registered for "set aside conservation reserve land" in the Midwest, South and Northeast. Except in California, it is registered throughout the U.S. for noncrop use (BASF, 1999).

Sethoxydim shows some selectivity among grass species, particularly among cool season grasses (Ross and Childs 1996). Sethoxydim should be applied early postemergence before the grass reaches the boot stage.

Paraquat: Trade Name: Gramaxone®: Paraquat applied at 0.5 to 0.7 lb./acre controlled greater than 97% of cheatgrass when applied during late April or early May (Whitson et al. 1993). Blackshaw (1991) reported that paraquat at 0.22 to 0.27 lb./acre controlled cheatgrass by 80-90% when applied up to the 3-5 tiller stage.

Paraquat is a contact herbicide that kills only the tissue contacted. Paraquat penetrates into the cytoplasm and causes the formation of peroxides and free electrons which destroy the cell membranes almost immediately (Ross and Childs 1996). Severe injury is evident hours after application and maximum kill is attained within a week (Ross and Childs 1996). If the plant is only partially covered with herbicide, only partial shoot kill will occur. Any new growth on the surviving plants will be normal in appearance, and foliar applications alone can only provide shoot kill (Ross and Childs 1996).

Glyphosate: Trade Names: Roundup®, Roundup Ultra®, Rodeo®, Accord®: Glyphosate applied when cheatgrass plants have 3-5 tillers at a rate of 0.16 to 0.18 lb./acre controlled cheatgrass by 80-90% (Blackshaw 1991). However a different experiment by Beck et al. (1995) using glyphosate at a much higher rate of 0.37 to 0.5 lb./acre resulted in only 80% reductions of cheatgrass within and between years. Glyphosate is a non-selective herbicide and will damage or kill desirable vegetation that it contacts including forbs and woody species. It should be applied in early spring after cheatgrass has established, but before perennial seedlings have emerged.

Glyphosate is an amino acid inhibitor (Ross and Childs 1996). It is a relatively non-selective compound that is used to control annual grasses and broad-leaved plants. Uses are limited to foliar applications only, as it is quickly inactivated in the soil (Ross and Childs 1996). Symptoms include yellowing of new growth and death within days to weeks (Ross and Childs 1996).

Imazameth: Trade Name: Plateau®: Imazameth can be applied at a rate of 0.24 to 0.75 lb./acre to newly established or existing stands of big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), Indiangrass (Sorghastrum nutans), sideoats grama (Bouteloua curtipendula), and blue grama (Bouteloua gracilis) to control cheatgrass, as well as other annual and perennial weeds (1,6). Plateau® is new herbicide that provides a broad spectrum of weed control for roadsides and native grasses in noncrop applications (3). It controls annual and perennial weeds without adverse effects on cool or warm season perennial grasses (1,2). Brian Winter, a TNC steward in Minnesota, used Plateau® to control leafy spurge (Euphorbia esula). He notes that it effectively controls cool season grasses and forbs, but leaves the warm season native grasses. It is labeled for use during the re-establishment of native grass prairie, but is not labeled for use in pastures, rangeland, or along streamsides (2).

Imazameth is an amino acid inhibitor that has a long residual life in the soil, and may leach into groundwater. It should not be used around streams and rivers (2). When applied, shoot meristems cease growth and roots tend to develop poorly (Ross and Childs 1996). Complete symptom development can be very slow and may take two to three weeks to develop (Ross and Childs 1996).

Fall Applied Herbicides: Fall herbicide applications should be conducted after cheatgrass seeds have germinated and are beginning to grow. Fall applications are generally used in cropland situations by farmers growing winter wheat or other cool season crops. However, sometimes these herbicides are used in pastures and rangelands.

Sulfometuron Methyl: Trade Name: Oust®: Sulfometuron methyl is a pre-emergence and post-emergence herbicide that controls many annual and perennial grasses and broadleaf weeds in noncrop areas (Dupont 1999b). Apply sulfometuron methyl at a rate of 3 to 5 oz/acre (0.2-0.3 lb./acre) for cheatgrass control (9). Masters (1998) found sulfometuron methyl has only a minimal effect on native perennial grasses and is helpful, when fall applied with imazapyr, in re-establishing native grasses.

Sulfometuron methyl is an extremely potent herbicide and can damage non-target vegetation if it is not applied correctly. Users should read the product label carefully before applying sulfometuron methyl to any area.

Atrazine: Trade Name: Aatrex®: In one experiment, atrazine at a rate of 0.54 lb./acre was the most cost-effective herbicide for decreasing competition of annual brome grasses and increasing yields of perennial grasses (Currie et al. 1987). In addition to suppressing cheatgrass, atrazine seems to stimulate protein production on native shortgrass range (Currie et al. 1987).

Atrazine is a pre-emergence, and to a limited extent early post-emergence, photosynthetic inhibitor that is mainly used in crops, but is sometimes used in pastures, rangeland, and noncropland (Ross and Childs 1996). It is registered for use on roadsides in Colorado, Kansas, Montana, North Dakota, Nebraska, South Dakota and Wyoming. In conservation reserve programs, Atrazine may be used in Nebraska, Oklahoma, Oregon and Texas (Novartis, 1999). Atrazine kills cheatgrass seedlings in the fall after they emerge from the soil while perennial plants are dormant. The following spring, the area is free of cheatgrass, and clear for the establishment of native perennial grasses. The half-life of atrazine in the soil ranges from 60-100 days. Atrazine is highly mobile in soil and has a high potential for groundwater contamination.

More information on chemical control of cheatgrass can be obtained from the Weed Management Library at 1-800-554-WEED.

* Mention of pesticide products in this document does not constitute endorsement of any particular material.