Warren: sugar sweetens the deal with cheatgrass control

Worland — Cheatgrass is an ongoing problem throughout the west and control options are always being explored. Eve Warren PhD, Worland BLM Natural Resource Specialist is using sugar treatments to reduce weed and cheatgrass growth.
“In the Big Horn Basin we have a lot of weeds. Several of them are native to the area and part of the flora and have evolved under conditions that make them very successful here. Most of the common native weeds are really difficult to treat because they’ve been here so long,” Warren explains, adding the Basin also has non-native, highly invasive weed species.
“There are also several naturalized plant species that didn’t start in this area but were brought in for agriculture, horticulture or other practices. It’s a matter of opinion if they are good or bad for the landscape,” she says.
Warren lists asparagus among those that are good for the landscape, explaining that while it isn’t native to North America, it now grows prolifically in part because it was cut and cleaned along railways where it was served in dining cars. She says dandelions are another example of a naturalized plant that can be considered good or bad.
Another naturalized plant common to the Basin and many other Wyoming landscapes is cheatgrass.
“It’s used to being here, we have ideal growing conditions and it’s invasive. It is a weed,” states Warren. “If we were to try to decrease or eradicate it, none of us would have any money left over. It is highly invasive and has no monetary value.”
The origin of cheatgrass is Afghanistan, Uzbekistan and Kazakhstan, explains Warren. It arrived in the United States mixed with crop seed, especially wheat seed from Russia. At one point it was sold in seed catalogs and advertised as a “10-week pasture.”
It is now being found at 6,000- to 7,000-foot elevations. There aren’t predators or parasites specific to the plant, and the seeds can survive for up to 11 years.
Control methods have been varied and extensive. Today they include mob grazing, where livestock are used to intensively graze the plant at specific times of the year, prescribed burns and herbicides, among many others.
“Lately the BLM has been looking more at herbicides. Roundup will kill it, and Rodeo can be used right up to the water’s edge. We can now use Plateau and it does suppress cheatgrass and perennial grasses. If you use Roundup there is the risk of developing a population resistant to the chemical,” says Warren.
Upon investigating other means of treating cheatgrass Warren found that native grasses prefer low nitrogen, high calcium environments, where cheatgrass prefers high nitrogen and calcium environments.
“Hypothetically, if you maintain a low nitrogen level, you should have an increase in native plants and a decrease in cheatgrass. The question becomes what can we do to make soils lower in nitrogen?” says Warren.
She found several papers from the 1980s and 1990s suggesting carbon can be added to the soil and will act like a thief to the micro-organism that fixes nitrogen, thus allowing slower growing native plants to thrive while suppressing the faster growing cheatgrass.
The first paper with a positive response was written in 1999 and mixed sawdust with sugar, then sprinkled it on the soil. The author sprinkled sugar at varying rates and the result was 75 percent decrease in diffuse knapweed and a 25 percent increase in Western wheatgrass.
Additional studies across the western states saw varying results in weed suppression and native plant response.
In 2005 a master’s thesis described a similar study that applied various sugar loads to soils at a maximum level of 909 pounds per acre. The result was a significant cheatgrass reduction in one year.
A 2008 field trial found that 909 pounds wasn’t needed and that the optimal level of application was anywhere from 200 to 600 pounds per acre.
Warren wanted to see if using sugar would work in loamy soils. She conducted studies at two separate sites in the Basin, near Worland and near Cody. Both locations had loamy soils and were grazed with cattle and sheep. At each location three four-by-four-foot plots were applied with varying sugar levels.
Initially vegetation was collected from each plot and sorted into native and non-native species and compared based on biomass. Sugar was then applied to each plot and watered to start the process. Two weeks later both locations got significant rains. The sites were watched for a year, then re-collected and compared.
On the Worland site the best response came from the plot applied with the equivalent of 200 pounds of sugar per acre. There was a large reduction in the number of weeds, and blue gramma and other grasses were coming up in the plot.
At the Cody site the plot treated with 600 pounds of sugar per acre was the most responsive. While cheatgrass levels were relatively stable, the native grasses were doing very well at the site also.   
Warren explains that sugar may not last as long in some soils or may seep through faster. Environmental and precipitation differences may have also led to the result differences.
When compared to herbicides, the sugar didn’t appear to have any effect on native species. However, the cost is much higher than that of traditional herbicide treatments. Sugar costs $18 for a 50-pound bag. To apply 200 pounds per acre costs $73 per acre. With Plateau the cost is around eight dollars per acre for the herbicide, not including application.
“It does decrease cheatgrass and increase native species, but the price is much higher. We can’t apply an herbicide within 200 feet of water, but sugar isn’t a problem so there could be a use for in specific areas. You can also apply sugar as frequently as needed. You could put it down twice a year where you can only apply Plateau once every two or three years,” explains Warren.
Sugar could become a viable weed and cheatgrass control option in some areas. It is a water-safe herbicide alternative that can be used after fires or on growing landscapes to reduce nitrogen levels and encourage native grass growth.
Heather Hamilton is editor of the Wyoming Livestock Roundup and can be reached at heather@wylr.net