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California’s bad romance with Bromus fuels wildfire

Non-native Bromus species, such as ripgut brome, grow fast and dry out quickly, becoming highly flammable.

When wildfires burn in California, people often call them forest fires or brushfires, but the odds are high that an invasive weed is an unrecognized fuels component, says a UC Agriculture and Natural Resources scientist.

“We have all of the nasty non-native Bromus species here in California, and the ubiquitous weeds are key drivers of increasing fire frequency,” said Travis Bean, UC Cooperative Extension weed science specialist based at UC Riverside.

Invasive, non-native Bromus species aggressively outcompete native plants, forming dense stands that grow fast and dry out quickly, becoming highly flammable. Fire can move rapidly through these dense patches of dry grass, especially during windy conditions or on slopes.

“When you have understory of dry Bromus or other weedy grasses, their ease of ignition can be the key link that allows fire to spread from areas like roadsides where ignition sources are plentiful to more pristine native plant communities,” Bean said. “Additionally, these fast-moving fires can throw embers that allows the fire to jump long distances or even reach high into the air, igniting structures.” 

The key to reducing the spread of invasive, non-native Bromus species or any annual weed is preventing the plants from producing seeds, says Travis Bean. Bromus tectorum or cheatgrass shown. Photo by Ron Vanderhoff

Identifying fire fuel

Bean would like to see the fuels in wildfires identified so people have a chance to consider managing these factors to mitigate the increasing frequency of catastrophic wildfire across the state.

With training, citizen scientists such as California Naturalists could help cities, counties, utilities and government agencies identify the invasive plant species that fuel urban wildfires.

“On a landscape scale, I would focus on managing Bromus anywhere human-caused ignitions occur,” Bean said. “Resources for management are scarce, and these species are widespread and can't be controlled everywhere they occur. Roadsides, hiking trails, and campgrounds are critical areas where people can start fires that spread, so It makes sense to concentrate management there.”

Bromus madritensis, or foxtail brome, is pervasive at lower elevations. Image source: Calflora
Cheatgrass (Bromus tectorum) is widespread at higher elevations, while ripgut brome (B. diandrus) and red brome (B. madritensis spp. rubens), also called foxtail brome, are pervasive at lower elevations. Along with other invasive winter annual weeds, they have successfully replaced large areas of the native vegetation in Southern California. 

“When I talk to land managers about these species, they recognize that some areas will have to be sacrificed and it may not be possible to eliminate these species from the landscape,” Bean said. They are prioritizing areas with smaller populations of theseinvasives where there is an actual chance to eliminate them, or are managing larger populations for containment so they don't spread.”  

Timing is everything

The key to reducing the spread of invasive, non-native Bromus species or any annual weed is preventing the plants from producing seeds, Bean said. “Whatever control method you chose, if deployed too early or too late, you gain nothing for considerable expense.” Too early and the plants may simply resprout, while too late and they will have already set seed and further contributed to next year's weed crop.

Herbicide is an effective and inexpensive means of control, though many prefer non-chemical methods. Hand pulling can be effective in small areas, but is discouraged for large patches due to the sheer amount of labor required and risks of actually spreading the weed seeds.

At Hopland Research & Extension Center, the River Fire burned right up to the fence line, stopping at the grazed pasture on left.

Another way land managers can try to prevent the weeds from spreading is by mowing or grazing with goats, sheep or cattle, Bean said, adding that using livestock can require more intensive management and proper timing is critical. 

“For mowing and grazing, the key is to wait until the plants have started to flower, but the seeds are not mature,” Bean said. “If you mow when there's mature seed, you'll just spread the seed and make the problem worse. And once the seedheads mature, grazing animals won't eat it.”

Prescribed fire is another option for containing invasive grasses, but is generally discouraged as there's a very high chance of exacerbating the problem. These Bromus species are very fire-adapted and tend to increase following burns. Prescribed fire should only be used by professional land managers. If this strategy is used, a burn plan, permits and training are essential. If not done correctly, prescribed burns may escape control and become wildfires, produce smoke that impairs visibility on highways, impacts air quality and human health, and damages native vegetation.

Prescribed fire is an option for containing invasive grasses, but may exacerbate the problem. A burn plan, permits and training are essential.

“Timing is everything,” Bean said, explaining the temperature difference between the plant and soil surface. “The grass has to be dry enough to carry fire, but not so dry that the seeds have fallen from the plant to the soil surface, where temperatures are much cooler than just a few inches up in the air where the seedheads are. Some research has shown this strategy to have been successfully used for certain invasive grasses like barb goatgrass (Aegilops triuncilias), but is not recommended for Brome species.”

He expects the changing climate to lead to more invasive plant species. “Invasive plants can be more resilient during drought and can quickly bounce back when rain returns, overwhelming natives,” Bean said. “And invasive species are often key drivers of wildfires and increasing fire frequencies and intensities, which prevents the recovery of native plants.“

 

Posted on Monday, July 22, 2019 at 3:38 PM
Tags: Travis Bean (2), Weeds (66), wildfire (153)
Focus Area Tags: Environment

Federal government proposes new fuel breaks to manage wildfire

The Federal Government has proposed spending $55 to $192 million to clear large swaths of land in the Western U.S. to create fuel breaks that slow the spread of wildfire, reported Brady McCombs of the Associated Press. The fuel breaks will be managed by the Bureau of Land Management in Idaho, Oregon, Washington, California, Nevada and Utah.

Fuel breaks are a useful tool if used along with other wildfire prevention methods that can keep firefighters safer and potentially help out in broad scopes of land because they are long and thin, said Lenya Quinn-Davidson, the area fire advisor for University of California Cooperative Extension. They can be especially helpful by providing perimeters for prescribed burns. But they must be in the right places, she said.

The article said the BLM has done about 1,200 assessments of fuel breaks since 2002 and found they help control fires about 80 percent of the time. The new fuel breaks will be 500 feet wide or less and created along highways, rural roads and other areas already disturbed.

Excavator clears understory vegetation as part of a fuel break. (Photo: USDA)
Posted on Monday, July 22, 2019 at 8:35 AM
Focus Area Tags: Environment

Weed control in lettuce

Figure 1. On left: Kerb at 3.5 pints/A applied at planting; On right Kerb at 3.5 pints/A + Prefar at 1.0 gallon/A applied at planting. The main weed is common purslane which was not controlled by Kerb because it was pushed below the zone of germinating weed seeds by the germination water.

Weed control in lettuce and other crops is a key issue this time of year. Purslane is particularly problematic and is adapted to warm conditions and can grow very rapidly especially during July and August. At times growers and PCAs are disappointed with the efficacy of Kerb on this weed. Kerb is...

Posted on Sunday, July 21, 2019 at 7:00 AM
Tags: Lettuce (18), purslane (2), Shepherd''s purse (1), weed control (82)
Focus Area Tags: Agriculture Pest Management

Exciting Research on Nematodes Published

UC Davis plant nematologist Shahid Siddique (Photo by Kathy Keatley Garvey)

If you read The Plant Journal today, you may have noticed the exciting research published on nematodes. And it has a University of California, Davis, connection. An international team of 10 scientists, led by plant nematologist Shahid Siddique, a former research group leader at the University of...

UC Davis plant nematologist Shahid Siddique (Photo by Kathy Keatley Garvey)
UC Davis plant nematologist Shahid Siddique (Photo by Kathy Keatley Garvey)

UC Davis plant nematologist Shahid Siddique (Photo by Kathy Keatley Garvey)

EVENT ANNOUNCEMENT :: Weedy Rice Workshop

weedy rice

Weedy Rice Workshop Thursday, August 1, 2019 10:00 AM- 12:00 noon (followed by lunch) Colusa Casino Chairman's Room This event is FREE, but you must register. Click HERE to register. Limited to 50 participants, so please enroll early. Seats will be filled on a first-come basis. Find out the...

Posted on Friday, July 19, 2019 at 3:07 PM
Tags: announcement (228), weedy rice (7)
Focus Area Tags: Agriculture

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