Weed of the Week: kochia

Kochia is one of the Prairies’ more damaging weeds.

And with three years of known resistance to glyphosate and many more Group 2 herbicides under its belt, the pest has found new ways to avoid farmer control.

It has also developed Groups 4 and 5 resistance in North Dakota and Montana.

Kochia, Kochia scoparia, is also known as summer cypress, burning bush and goosefoot.

Recent flooded conditions aided the spread of the plant due to its ability to producer up to 25,000 seeds, if allowed to reach maturity.

The tumbleweed has one of the most effective seed spreading systems in agriculture. Those who discover glyphosate tolerant versions often see the tumbleweed’s travel pattern as a green, meandering stripe through their field, especially in chem-fallow situations.

A serial out-crosser, something it shares with humans, each seed and plant can be unique. As a result, with thousands of seeds, kochia has the ability to generate the right mutations to form the basis for herbicide tolerance selection.

In drought, roots will extend as far as three metres into the soil hunting water and nutrients.

The summer annual broadleaf arrived in Canada as an ornamental plant with European settlers. It was also known in Europe as providing forage for livestock production in times of drought.

It is capable of growing up to two metres in height when competing with tall crops, such as corn or durum wheat.

When little, the pest has an erect, multi-branched stem and can have purple stripes. The hairy, grey-green leaves look dusty.

The kochia flowers lack petals and are made up of small, green sepals. Each of the tiny flowers becomes a brown, oval seed with a groove on the sides. The burning bush term comes from plants that turn a bright red after seed-set.

It can be a serious issue for pulse crop growers, because peas and lentils can become tied up in the weeds and even after desiccation, they can be a challenge to harvest.

Kochia’s seeds have a short life in the soil, so control can be achieved in a single year. They germinate quickly in the spring and are cold tolerant.

Just 21 plants per sq. metre reduce wheat yields by one-third. In flax and pulse crops, the plant can be devastating, choking out broadleaf crops for sun and moisture.

As a livestock feed, the plant is high in protein and carbohydrates and produces well under the toughest conditions.

It contains saponins, alkaloids, oxalates and nitrates in amounts that can be toxic to livestock, so it must not exceed 50 percent of the diet.

Due to the Group 2 resistance, using other Groups of broadleaf herbicides is critical to its control.

Glyphosate, when applied pre-harvest, gives good control of sub-mature plants and seeds, other than those that are tolerant.

In cereals and flax, bromoxynil with MCPA can be effective or tank mixed with other products. For flax Fortress is an option.

Early post-emergent and burn-off applications can help control this noxious pest. Adding tillage and mowing are also effective.

Kochia seeds can end up in and are tolerated so some degree in most seed lots. Luckily, there are a wide variety of herbicides to control the pest in cereals.

In peas, solutions are harder to come by. Edge and Authority, with or without Charge are the label options. Clearfield options in lentils provide control and Edge can be used in fall. Herbicide tolerant canola is an effective strategy for that crop. Edge, again, can used with canola.

While control can be accomplished in a single year, attention needs to be paid to herbicide Group rotations.

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