Weed of the Week: green foxtail

If there is one thing that setaria veridis doesn’t enjoy, it is tillage.

Luckily for the weed, farmers have been reducing that particular agricultural practice for more than two decades.

Green foxtail, as it is best known in Western Canada, has become a serious pest for prairie producers.

It once showed up almost exclusively in the region’s black soil zone, but it has made a steady march south and can now be found across the brown soil zone.

The weedy millet’s tiny seeds are not only good at spreading, but they can also hide in grain shipments.

Green foxtail is recognized as a yield robber and is registered as a noxious weed in 46 American states and in Canada.

The plant doesn’t compete well for resources, but it can find a home relatively easily in fields with wider row spacings.

When left to mature, green foxtail’s fibrous root system can scavenge nutrients even in tough and droughty conditions. The plant reproduces from seed and generates 350 to 500 seeds per head with as many as 10 heads per plant.

Cultural control involves ensuring that the weed doesn’t live long enough to set seed and squeezing it out through early seeding or planting a three year forage rotation. However, the latter isn’t an option for many strictly grain producers.

Green foxtail prefers warm soil conditions, and the seed doesn’t germinate well on top of the soil. As a result, spring harrowing will help put it into the right zone to get it growing and then put it into the path of spring herbicides.

American grain growers have given it a variety of names — bottle grass, bristlegrass, pigeon grass and wild millet.

Foxtail first appears as a single, tiny, green leaf running parallel to the ground. It is still small at the four leaf stage and can be confused with other cereals.

Tiny fibres where the leaf meets the stem before heading are tell-tale signs that this is not a crop.

The good news is that herbicide control is possible with most crops, but oats has only one registered solution for suppression: linuron with MCPA ammine. This works with other cereals as well.

The products that are available in barley include pinoxaden, Axial, tralkoxydim (available in a mix with bromoxynil and MCPA as Achieve Liquid Gold or for application with an adjuvant under the trade names Liquid Achieve, Bison or Marengo), fenoxaprop (under a variety of names including Puma), triallate and trifluralin (Fortress), Trifluralin (Treflan, Rival and Fortress) and pyrosulfatole mixed with fenoxaprop and bromoxynil (Tundra).

Most of the barley choices are also registered for wheat, as well as clodinafop (under a variety of names including Horizon and various mixes such as Harmony) and flucarbazone (Everest or Sierra). Suppression is available with pyroxsulam (Simplicity) and thiencarbazone (Varro).

Clear-field wheat offers those control choices.

Most products that control cereals in broadleaf crops are effective, but it can be tricky to get the crop staging right.

Foxtail likes warm soil and can germinate mid-season, so pre- or post-harvest applications of glyphosate or similar products can reduce chance of making seed.

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