July 15th, 2015
How to beat the ‘cheat’
By Donald Shoderbek
Donald F. Schoderbek is a Range Specialist with the CSU Extension Peaks & Plains Region, serving 32 counties in Eastern Colorado and the San Luis Valley. He is based out of the Northeast Regional Engagement Center in historic downtown Sterling.
I was recently driving around with a producer south of Iliff, and we came upon the site of a cheatgrass invasion in his pasture. This wheat-colored, short-statured, winter annual grass is a problem weed in all 50 states, as well as many Mexican states and all 10 Canadian provinces. In Colorado, cheatgrass is listed as a noxious weed. As such, counties possess legal authority for regulation and management of this plant. This weed is especially prevalent on roadsides, railway and utility right-of- ways, and disturbed areas. Increasingly, it is also dominating large rangeland pastures, where it ‘cheats’ the native prairie of valuable nutrients and moisture.
Like many High Plains plants, this one has a colorful word history. Cheatgrass’ Latin name is Bromus tectorum, due to its tendency to grow in decaying/old sod roofs. Its Latin root is ‘tectum’, for roof, and ‘bromus’, for oats; hence the name Bromus tectorum, or “grass of the roofs”. This speaks to cheatgrass’ exceptional competitive ability. Other names include downy brome, early chess, wheat- thief, and Mormon oats. (Authors note: for the remainder of this column, I will use the Latin name B. tectorum for clarity.)
B. tectorum is originally native to the Near East. The first reported collection of B. tectorum in the USA was in the 1860s, but recent genetic evidence suggests an entry into the continent in the 1790’s. The grass was often used as packing material and bedding, and quickly spread across the country with Western settlement. As an annual grass, which dies each year, it has a distinct competitive advantage over the perennial, persistent native prairie. The historic droughts of the late 20th and early 21st century have also created near-ideal conditions for expansion.
In the last 30 years, B. tectorum has taken over huge areas of the West. Estimates for infestation in the US range from 50 – 150 million acres, an area about twice the size of Colorado. This has had a profound ecological and economic impact, especially in the Great Basin. Universities and federal agencies have aggressively pursued management and control methods, with some success. Because of B. tectorum’s ability to germinate either in the fall or the spring, control can be especially Pre-emergent herbicides, often a rancher’s first resort, may not be effective if the plant has germinated in the fall and overwintered.
With B. tectorum, any control program will likely be a war of attrition. Each individual plant produces ~500 seeds per year, and some vigorous stands have been documented to produce > 10 million seeds per acre (i.e. several seeds per square inch). However, the seedbank is generally not persistent, often only lasting 2 – 3 years. This means that with a sound management plan, effective control can be completed in a manageable time scale. Several control methods have been shown to be effective in our region. If you truly want to beat the ‘cheat’, here are some helpful ways to go about it.
The old saying “an ounce of prevention is worth a pound of cure” is especially true in this case. Common sense practices include: buying clean pasture/crop seed, cleaning equipment and tires frequently, making sure manure is not contaminated with seed, and practicing good grazing management. Working with your neighbors and county weed management districts is another great place to start
Believe it or not, B. tectorum actually has excellent forage value prior to seed set. Plants often test in the 10 – 17 % crude protein range, which can provide top-shelf forage for calves in the spring. However, once seed set occurs, the plants quickly drop in palatability and quality. The most effective grazing system is called mob grazing. In this system, a dense herd of livestock is ‘pushed’ across the land while they graze, usually by a combination of fencing, dogs, and riders (similar to the ‘grazing trails’ of the 19th century). This high-intensity, low-frequency system can reduce seed production by more than 90%, as well as providing forage at a crucial time of year for cow-calf systems. However, properly timing the grazing can often be a challenge, due to the short window of palatability.
Several herbicides can successfully control B. tectorum.
This is the most widely-used herbicide for tectorum control. It works by stopping amino acid synthesis in the grass. It is most effective when applied between emergence and the 3 – 4 leaf stage. When properly applied, this herbicide generally does not have a negative impact on native grasses. It also has a relatively low health risk to humans and animals.
This is a very standard herbicide, and is widely used It also stops amino acid synthesis. When used for B. tectorum control, a light mix rate is used to minimize harm to the native prairie. However, some harm to the native species is likely to occur. Timing the application to coincide with active B. tectorum vegetative growth is also critical, proving another limitation.
Paraquat (Many trade names).
This is the ‘nuclear option’ for tectorum control. Paraquat has been used extensively by the DEA and military forces as a defoliant. It is a salt that works by killing any green plant material on contact. When used, take care to avoid any exposure for > 1 year to humans or animals – it is highly toxic. However, it is very effective, and may be the last (or only) resort. Interestingly, it is also widely available in hardware stores as a weed spot treatment.
Cheatgrass Management Handbook. 2013. Published jointly by UW and CSU extension. Available at: http://www.wyomingextension.org/agpubs/pubs/B1246.pdf
Cheatgrass Fact Sheet. 2003. Published by Colorado State Parks.Available at: https://cpw.state.co.us/Documents/ResourceStewardship/DowneyBrome.pdf