Weed Watch: Fickle winter weather favors shifting weeds

Published on: 14:49PM Apr 23, 2013
Mother Nature is keeping winter wheat farmers on the edge of their seats as they watch the weather and plan spring weed management programs. A remarkably warm early winter gave growers high hopes for crop yields, coupled with concerns about weeds benefitting from the same good fortune. Weed competition is often a top issue for wheat growers, as it robs plants of precious water, nutrients and sunlight; however, it can be especially devastating during drought years, when dry conditions have already taken a toll on crop yield and quality. To complicate weed predictions further, the temperature freezes that took hold in the middle months of winter, along with the lack of consistent insulating snow cover, may already be giving spring weeds an advantage.

WeedWatch wheat

North Dakota State University associate professor Kirk Howatt explains, "Due to the open snow cover we’ve been seeing this winter, weeds may get started earlier this year. When the ground is showing, we sometimes get a flush of weeds that come up and become established." Howatt says that this winter the Northern Plains seems to be in a weather cycle fluctuating from cold to exceptionally cold temperatures. While the weather trend has been steady for a few weeks, he adds, "There have also been years when February was warm enough for early emerging spring annuals, or later emerging winter annuals to become established, even when the ground was still fairly frost-bound. Scouting over the next few weeks will help us determine if that was the case this year, too."

Syngenta recommends diversity, integrated management to combat weed competition
Jill Herold, a Syngenta agronomic service representative in Montana, advises growers to use an integrated approach for spring weed management. "Utilizing chemical products alongside tried and true cultural practices has become the key to managing weed competition."In regard to weed resistance, Montana is in a similar situation to the Pacific Northwest (PNW) region. According to Herold, this year the main weed threats to western winter wheat in the Northern Plains are kochia, foxtails, barnyardgrass, wild oat, brome grasses, and most recently, hawksbeard.

"Hawksbeard acts like a winter annual," she explains, "so it’s going to be one of those early weeds and we’ll have to watch for its emergence. It can be easily mistaken for prickly lettuce or several other broadleaf weeds, so we’ll have to keep an eye out for it."
Herold recommends applying Axial® XL herbicide to protect against foxtails, wild oat and barnyardgrass, while using Axial® Star cross-spectrum herbicide for its unique strength against kochia. For difficult grasses in the brome family, Herold suggests that using Sierra can help, adding that it is also very effective on wild oat and foxtails.

Weather and weed forecasts

In the PNW, Syngenta agronomic service representative Donald Drader from Washington is seeing similar weather patterns. "The weather this year has been cold," he says, "with less than average snow fall to date. Hopefully we can anticipate some additional precipitation as the weather warms up so we have adequate soil moisture."
Drader explains that wheat growers in the PNW are monitoring their fields for tough-to-control grasses such as wild oat and Italian ryegrass. Since grasses are showing increased resistance to Group 1 herbicides, Drader says, "Wheat growers need to look for additional tactics to manage their resistant grasses in the fall. In addition to their crop rotations and fall tillage practices, they may want to make an application of burndown products, such as Touchdown® brand herbicides or Gramoxone® SL 2.0 herbicide after the grasses have germinated, but prior to wheat emergence. They can also utilize fall-applied herbicides with different modes of action and follow up in the spring with grass herbicides like Axial XL and Sierra, or a grass-broadleaf herbicide like Axial Star.
He adds, "Broadleaf weeds are also being carefully watched, especially in areas with high resistance. Growers and retailers are doing an excellent job of tank mixing two or more broadleaf herbicides to control a wide spectrum of different weeds." Weeds to watch for in the PNW include: wild oat, foxtails, Italian ryegrass and brome grasses.

Investing in the future to grow more wheat
Herold also encourages growers to keep an open mind about cultural practices, such as tillage and crop rotation to stop resistance from evolving. "Tillage is definitely something to consider, though it depends on the area and the moisture." Herold says growers should consider adding it to their program, not necessarily every year, but as a part of the long term plan. "We are relying on one solution when we should be looking at them all," she explains. "We need to blend in more cultural practices to find an innovative approach for the challenges the coming years will bring."

This winter’s fluctuating temperatures and inconsistent snow cover are complicating weed management plans for spring, however regardless of geographic region, wheat growers are focusing on similar strategies. While a large part of planning spring weed management has been learning from the challenges and successes of the past, in recent years growers have been pushed to incorporate new solutions to growing problems like kochia management and herbicide resistance.
Syngenta and university experts recommend an integrated approach to weed management that incorporates both chemical application and cultural practices such as crop rotation, tillage and thoroughly cleaning farm equipment to prevent the spread of seeds. By being diligent with a wide variety of management practices, winter wheat farmers across the Northern Plains and PNW can grow more wheat by eliminating weed competition no matter what Mother Nature has up her sleeve.

©2013 Syngenta. Important: Always read and follow label instructions. Some crop protection products may not be registered for sale or use in all states or counties. Please check with your local extension service to ensure registration status. Gramoxone SL 2.0 is a Restricted Use Pesticide. Axial®, Gramoxone®, Sierra, Touchdown® and the Syngenta logo are trademarks of a Syngenta Group Company.