NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665

June 17, 1999

Flax Acreage Offers Weed Control Challenge

Flax acreage will be up in North Dakota this year because of the favorable loan rate and delayed planting caused by wet conditions in some regions. Weed control in flax is an important concern for growers, according to a North Dakota State University agronomist.

Uncontrolled weeds can be a serious problem in flax, says Duane R. Berglund, NDSU extension agronomist. Because flax does not shade the ground as much as cereal grains do, weeds have an excellent chance to develop in flax fields.

Some weeds, like wild buckwheat and redroot pigweed, use large amounts of nitrogen and rob the flax crop of needed soil nutrients. In addition to reduced yields from competition for nutrients, weeds also cause losses from dockage in flaxseed shipments. Dockage amounts to thousands of dollars annually, Berglund says.

Herbicides registered for use on flax include trifluralin, MCPA, bromoxynil, Poast and sodium chlorate (Defol) as a preharvest desiccant.

Trifluralin can be fall applied for foxtail and broadleaf weed control on fields to be planted to flax. Planting flax would be a good option on land that was fall treated and intended for canola, says Berglund.

Bromoxynil controls wild buckwheat, volunteer sunflower and most broadleaf weeds. Some leaf burn may occur on flax at high rates or if high temperatures follow application. Mixtures of bromoxynil and MCPA may cause flax injury if applied during hot, humid conditions.

MCPA applied to 2- to 6-inch tall flax controls many broadleaf weeds. MCPA amine at rates higher than 0.5 pint per acre or MCPA ester should be used for improved kochia and Russian thistle control in flax.

Poast plus an oil additive will control annual and perennial grasses and would be useful to control volunteer grains in flax, Berglund says. This treatment is less effective if the grasses are under drought stress. Poast plus oil can be tank mixed with either bromoxynil alone or with MCPA ester. Some leaf burn, retarded growth and delayed maturity can occur with the tank mixes, and reduced grass control can also result. Poast must be applied prior to flax bloom and 75 days or more before harvest.

Berglund strongly advises against using 2,4-D in flax. "It's not labeled, and excessive injury will occur," he says.

With all herbicides, consult the label before use. Detailed weed control information can be found in the 1999 edition of the "North Dakota Weed Control Guide", NDSU Extension Service publication W-253.

###

Source: Duane Berglund (701) 231-8135

Editor: Gary Moran (701) 231-7865