Managing Annual Bromes
Herbicides, grazing and fire can be effective tools.
by Kindra Gordon for Angus Productions Inc.
CASPER, Wyo. (Dec. 2, 2009) — Research trials conducted by Agricultural Research Service (ARS) scientists at the Fort Keogh Livestock and Range Research Lab in Miles City, Mont., indicate that timely herbicide applications, grazing and fire are each effective tools in managing Japanese and downy brome. That was the message ARS range ecologist Lance Vermeire shared with attendees at the 21st Range Beef Cow Symposium in Casper, Wyo.
"Control of annual bromes requires reduction of the seed bank over time," ARS Range Ecologist Lance Vermeire said. "If we don't manage the seed bank, it will snap back quickly."Vermeire told producers that managing annual bromes is important because these species can affect forage quality on rangelands and compete with more preferred perennial grasses.
“Control of annual bromes requires reduction of the seed bank over time,” Vermeire said. “If we don’t manage the seed bank, it will snap back quickly.”
Vermeire discussed the following three strategies for control:
1) Chemicals. He noted that traditional herbicide applications, such as Roundup®, can be challenging because they are very sensitive to timing and can reduce desired forage species if applied at the wrong time. Thus, ARS researchers instead have conducted trials applying herbicides more traditionally used for broadleaf weed control — such as 2,4-D, picloram (Tordon® and Grazon®) and dicamba (Banvel™ and Brush Buster™) — to see the impact on annual bromes.
Vermeire explained that these herbicides have been shown to cause seed sterility in cereal crops if applied during seed development. And, similarly, the researchers found that dicamba and picloram both gave reductions in viable seed when applied to brome plants. The 2,4-D had no effect.
In a field-trial setting, the broadleaf-applied herbicide was effective at reducing seed viability by as much as 95%. Vermeire said that it was effective if applied at the internode, boot or heading stage, which allows producers some flexibility for application timing.
2) Grazing. From the ARS trials, Vermeire shared that close grazing of brome — to about a 3-inch height — reduced productivity of plants by 50%. Grazing brome in June seemed to be the most effective timing.
He suggested producers graze brome-infested areas in mid-spring. “That is when forage quality is highest on the brome plants so there is some forage value,” he said, “and that is when the plants are most susceptible to seed reduction.”
He did caution that repeated heavy spring grazing can increase brome, so he also warned, “There is a delicate balance between intensity and timing.”
3) Burning. Research using fire as a control tool is also offering encouraging results. “Fire provides direct consumption of all of the seed that is above the soil," Vermeire said, and shared study results in which fire reduced the amount of seed by 90%.
Burning in the summer, fall and spring were all effective timings, he noted. Fire promotes a positive response from desirable perennial grasses and forbs in addition to reducing the annual brome population and seed bank. He cited one study where the population of western wheatgrass doubled just two years after a burn.
Vermeire noted that future research will look at timing brome control strategies to make them even more effective and long-lasting. As an example, he said, “If we have a wet fall, we know that is when cheatgrass germinates, and we can prepare to follow grazing or fire treatments in the spring with chemical treatments to give a one-two punch to significantly reduce the annual brome seed bank on rangelands.”
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