What You Need To Know About Kochia - PulsePoint
April 16, 2019
Strategies to handle this genetically diverse and herbicide-resistant weed
by Noelle Chorney
Kochia is a drought-tolerant, prolific seed producer with increasing herbicide tolerance — and it was the number one weed issue last year. Here is what you need to know about controlling it.
“Kochia’s strengths as a weed come from many factors and include its ability to grow in adverse environments such as hot, dry, and high salinity,” says Saskatchewan Pulse Growers Agronomy Manager, Sherrilyn Phelps. “That makes it an extreme opportunist to less competitive crops such as pulses — particularly lentils.”
Kochia both self-pollinates, and cross pollinates, so plants in the same area have great genetic diversity. Several regions on the prairies have herbicide-resistant plants. Resistance to Group 2, 9, and 4 herbicides as well as combined resistance has been widely documented. Resistant genes pass quickly from plant to plant in regional plant communities.
Kochia does have some weaknesses that can be exploited. Phelps says, “It has an annual life cycle. It only produces seed in the first year, so controlling seed production will help reduce seed for following years. Kochia germinates early in the spring, making it a great target for good weed control prior to crop emerging.”
With increasing herbicide resistance across the continent, however, integrated measures need to be considered.
Mitigate Saline Areas
Provincial Specialist, Weed Control with the Saskatchewan Ministry of Agriculture, Clark Brenzil says, “Kochia on its own merit is not horribly competitive in healthy soils. It grows in areas that have poor crop cover due to drought or salinity. Salinity is a bigger problem when we are transitioning from a wet period to a dry period. When water evaporates, the salt is left behind. These areas will not support crop production and they essentially create a kochia nursery.”
Weed specialists recommend taking these saline areas out of crop production by seeding them to saline tolerant perennial forage. “You are already not getting a great return, if any, for what you are putting into that area,” says Brenzil, “so even though it is easier to seed it all at the same time, it does not make sense. Stop wasting inputs in an area where adding more salts (fertilizer) will only make it worse.”
“Kochia is a solvable problem,” says University of Saskatchewan Professor of Plant Sciences Dr. Steve Shirtliffe. “But we may need to change the way we think about site specific agriculture. If we limit seed production in the saline areas, we at least can limit what is coming from our field areas.” Researchers will soon be mapping salinity and kochia appearance to demonstrate how managing saline soils can help control the weed.
Competitive Crop Rotations
If you have a kochia problem, consider a rotation of winter cereals or forage, which are more competitive with kochia. Kochia can also be cut along with a hay crop and fed to livestock1 to prevent seeds the following year. When you start with a clean field, your pulse crops will have a better chance.
“Kochia is susceptible to competition in non-saline areas when it is young. In nonsaline parts of the field, increasing crop competition through increasing seeding density and narrowing rows will be effective,” says Shirtliffe.
Stop Seeds Before They Start
Kochia sets seed late in the year, so can be mown, tilled, or grazed in its vegetative state to prevent seed set. If you have off-field sites of kochia that could spread, consider controlling them as well. Mechanical seed destructors are an option in-crop at harvest, but good old mowing and hand pulling before the plants set seed can be just as effective.
“Tank-mixes with glyphosate for spring burn-off are important for controlling early flushes of seedling growth,” says Phelps. “Use of soil residual herbicides with activity on kochia can also provide longer-term control to keep populations down. For pulse crops there are limited in-crop options for kochia management, which means it is critical to plan ahead to control the weed prior to crop emergence.”
Emerging seedlings in non-saline areas can be mechanically controlled using a rotary hoe. Harrowing is important when using granular pre-plant incorporated soil active herbicides such as Edge®, to ensure the granules make contact with the soil rather than catching in plant residue on the soil surface.
A fall application of Edge® in low tillage fields allows time for the granules to break down and integrate with the soil. “When the soil is cool and light levels are low, Edge® (Group 3) will not be lost to gassing off or photo-degradation as it can in spring. Freeze-thaw cycles help the granules disintegrate over the winter, and with one more pass with harrows in the spring, it will be ready,” says Brenzil. He advises producers using soil active ingredients to follow re-cropping options carefully.
Pre-emergent surface (PRE) herbicides can be applied at the same time or within a few days of seeding. Some may also be applied the previous fall. See the chart for the options that will work for your pulse crop. Check the product label for details.
If you have a kochia problem, plan ahead and use all the cultural, chemical, and mechanical tools at your disposal. With careful management, you can dramatically reduce the occurrence of kochia within one growth cycle.
1 Kochia has similar nutritive value to alfalfa, but has high oxalic acid levels. Keep kochia rations below 40 per cent.
Get to Know Kochia’s Adaptive Traits
- Germinates in dry conditions (at moisture levels where wheat will not germinate)
- Thrives in saline soils
- Seedlings have tiny hairs that protect the leaves from moisture loss, but also blocks herbicides
- Produces up to 30,000 seeds per plant
- Little-to-no seed dormancy/high germination rates
- Spreads long distances as a tumbleweed
- Is highly outcrossing, resulting in high variation in plant morphology/adaptable to environment