Control bromes effectively through grazing, fire and chemicalsWritten by Christy Hemken
It’s those characteristics that make the grasses difficult to control, a subject Lance Vermiere of USDA’s Agriculture Research Service at Ft. Keogh near Miles City, Mont. addressed at the early December Range Beef Cow Symposium in Casper.
“If they don’t get the fall moisture, you won’t have bromes,” said Vermiere, noting the grasses germinate in the fall. “Some will germinate the first year the seed’s produced, but most will germinate the second fall. That gives us management opportunities we don’t get with a lot of other species.”
However, he said bromes are very erratic. “You can’t count on them,” he said. “Plus, there’s a brief window where they’re high in forage quality, but it’s so brief it’s difficult to take advantage of it. Quality factors are dependant on precipitation, disturbance, litter and temperature, among other things, and you can’t count on any given level of production from these species.”
Because annual bromes mature so early in the growing season they bring overall forage quality down and compete with the preferred forage species. “Japanese brome is very deficient in forage quality most times, and it’s higher quality than cheatgrass,” said Vermiere.
However, he noted the seedheads of Japanese brome are high quality, so livestock may selectively graze them, which can be used to the advantage of livestock producers. “It’s fairly good stuff for a brief period,” he said.
Vermiere’s talk highlighted research results in controlling bromes through grazing management, chemical control and fire.
“With any form of control we’re talking about control of the seedbank,” he said. “A lot of things we do may have a short-term effect, but if we don’t reduce the seed bank it’ll snap back quickly.”
He said control through herbicide requires specific timing. “With glyphosate, or Roundup, you have to apply it when the other preferred species aren’t actively growing,” he explained. “We’re looking at using growth regulating herbicides like 2,4-D that would normally be used to control broadleaf weeds.”
“From a history with row crops, people have accidentally sprayed wheat with 2,4-D and noticed a lot of the seeds go sterile,” said Vermiere.
A study applied 2,4-D, Picloram and Dicama to Japanese brome at different stages of growth – seedling, internode, boot and heading. Although no results were seen with 2,4-D, Vermiere said there were sharp reductions in the percentage of viable seeds with the other two herbicides.
“There was 100 percent reduction in viability when they were applied late when the plants were heading out,” he said. “That’s encouraging, but it was also in a greenhouse situation under a controlled environment.”
When the trial was taken to the field slightly different herbicides were used – aminopyralid .5, aminopyralid 1 or picloram.
“What we saw was even better than the controlled situation,” noted Vermiere. “Anywhere from 61 to 70 percent of seeds were viable at first, and after herbicide application we had five percent viability, and generally less than two percent.”
Vermiere said it didn’t matter at what stage the herbicides were applied; there was always good control. “That really broadened the window during which we can apply control,” he said.
He said that broader window is important because often brome production isn’t synchronized, with later plants emerging.
Regarding the use of grazing or clipping as control, Vermiere said in a controlled situation frequently clipping plants to six inches or three inches reduced their productivity. “It does work,” he said. “Graze down close to three inches and you’ll reduce productivity. The bromes will still use resources, but they’ll use less of them.”
“There are much higher amounts of brome in pastures rested in the spring and allowed to build up litter,” he explained. “Litter can increase soil moisture near the surface, and that can allow brome plants to germinate when they might not have otherwise.”
Concerning the fact that animals will selectively graze the seed heads, Vermiere said some work has shown grazing in June when the plants head out can reduce the soil seed bank by 50 percent.
“If you have a brome problem in an area, we recommend you graze that during early spring and going into June, when you’ve got the highest forage quality and when the plants are most susceptible to removal of their flowers and can’t produce more seeds,” he said.
He said researchers have also determined repeated early spring grazing can reduce brome growth, suggesting those pastures be used for calving, but noting that will also affect the preferred forage species. “It’s a delicate balance in intensity,” he said.
The last control measure Vermiere discussed was fire. “We’re encouraged with a lot of results from fire control,” he said. “Fire has multiple effects on brome.”
He said one is direct consumption of seeds in the canopy, litter layer or soil surface. However, a grassland fire won’t affect seeds buried. “When the plants first germinate they’re susceptible as seedlings to direct mortality, and fire can also reduce litter so they won’t germinate in the first place.”
Fires were conducted in spring, summer and fall. “Fire in any season reduces the density of bromes by almost 50 percent,” explained Vermiere.
“More than the season, control by fire depends more on fire conditions,” he added. “Just because you can get a fire doesn’t mean it’ll burn all your fuel.”
“If you’ve got dry enough fuels to carry a fire down to the soil surface, but the litter layer is moist the fire won’t burn as well and it will reduce the ability to consume seeds in the fire,” he said. “That’s why we get better results from summer fires.”
Not only have researchers seen reductions in Japanese brome and cheatgrass following fire, but it also promotes a positive response from the preferred species.
Although cheatgrass is moving into Wyoming, Vermiere said he doesn’t think the Great Plains will turn into the Great Basin with a cheatgrass-dominated grassland. “It’s a serious issue, but the difference between the two sites is what species are available,” he said. “The perennial sod-forming grasses tend to be able to compete better than the bunch grasses farther west.”
Although all three methods of chemical, grazing and fire provide effective control, Vermiere said they each tend to be short term.
“We’re looking at integrating and timing them to coincide with weather events,” he said. “It’s something we’d like to do in cooperation with range management, because the bromes germinate in the fall and we can predict months ahead of time what will happen.”
He said he’s looking at following grazing and fire treatments with herbicide treatments to rapidly reduce the brome seedbank. “Brome seeds are short-lived,” he said. “They’re viable two or three years and after that it’s greatly reduced. These three methods together could give us a one-two punch in control.”