Weed of the Week: field dock

Field dock’s single, sometimes forked, large taproot has allowed the weed to flourish since tillage was reduced in Western Canada.

It pokes out of the crop where the sprayer missed, and at first the green flowers and stalks aren’t too noticeable. However, it later turns red and brown and sticks out like a sore thumb.

Formally known as Rumex pseudonatronatus, it is the more common of the three Rumex found in Western Canada. Curled dock tends to be a bigger problem in Eastern and Central Canada, while its twin, western dock, is less of a problem.

Many broadleaf herbicides will control the weed, but timing is critical.

Dock can also be controlled with vertical tillage or shallow tilling after harvest and in low areas that escaped earlier spraying.

It can escape post-emergent control, especially when seeding gets an early start and soil remains cold, such as this year.

The large, curly leaves quickly shade the surrounding plants, which reduces crop yield, or at least costs the producer another pass with the sprayer.

The weed can be tough to tame if it escapes spring control.

Glyphosate and glufosinate are effective, so herbicide tolerant systems provide an option. Clearfield crops also work well.

Spot spraying glyphosate at 2.83 to 4.86 litres per acre of the 360 grams per litre product in 10 gallons per acre of water works if the weed reaches the bud stage.

Group 4 chemistries are effective.

Spot applications of dicamba (Banvel 2) can be used if the weed establishes in rangeland, as long as plenty of water is used to carry it.

Producers are advised to use .92 litres per acre of Banvel II in 10 to 20 gallons of water per acre on actively growing weeds for top growth control.

Picloram with 2,4-D (Grazon) and aminopyralid and 2,4-D (Restore 2) can also be used in pasture situations with the right plant populations.

An application of 500 grams per litre of MCPA amine or 2,4-D amine applied at .45 to .7 litres per acre will control top growth.

Dichlorprop and 2,4-D at .71 litres per acre suppresses the weed when plants are less than 50 millimetres tall.

Semi-mature plants are slow to react to systemic herbicides. Agronomists suggest waiting a couple of weeks to mow if sloughs are being controlled with herbicides to ensure that the weeds are killed.

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