Kochia: What Can Western Canadian Farmers Do to Manage This Problem Weed?
Kochia has become a troublesome weed for growers across western Canada, and the problem seems to be getting worse. In the article below is information on understanding kochia and suggestions on how to manage kochia long term.
Kochia is a member of the goosefoot (Chenopodiaceae) plant family (like lambs-quarters) and is a subfamily of Amaranthae (amaranth family). Kochia was originally introduced to North America from Eurasia as an ornamental plant as gardeners liked the rich red color of the plant in the fall. It eventually spread throughout North America where it is found primarily in grassland, prairie and desert scrub ecosystems. It has been used for erosion control in eroded soils and saline areas and provides forage for grazing.
What Makes Kochia So Adaptable to Western Canada
- Kochia is very drought, frost and heat tolerant.
- Seeds can germinate in drought conditions with little soil moisture.
- Greater than 75% of kochia seed germinates within a broad soil temperature range, 4 – 41 C, with an optimum range of 15-20° C, however it can emerge when average minimum daily soil temperatures are as low as 2.8 C, and seedlings can survive temperatures as low as -12 °C.
- Kochia seed has very low dormancy – approximately 90% of seed will germinate the following year. Less than 5% of the seed survives 2 years in soil.
- It tolerates highly saline soils and can germinate and grow in salt concentrations as high was 10,000 ppm and in soils with a large pH range of 2 – 8.
- It is a C4 plant, which means it can fix carbon more efficiently in drought, high temperatures, and limitations of Carbon dioxide or nitrogen resulting in higher photosynthetic capacity in conditions with higher temperatures, less water, and available nitrogen.
- It can grow up to 7 ft. tall with competition, or 3-4 feet without competition.
- It is grown as a drought resistant forage in US Southwest (“poor man’s alfalfa”) and is known as a food source for wildlife in some areas because it contains a higher level of protein and oxalate than most other grasses and fodder plants. However, it’s use is limited by toxicity if consumed by livestock in large quantities.
- It requires relatively large amounts of nitrogen (100 to 250 lb/acre); however, if too much nitrogen is applied at once, toxic levels of nitrate may accumulate in the plants.
- It has a built-in population control mechanism – auto-allelopathic – which means it retards the growth of other kochia plants that grow too close.
- Kochia stems are biologically programmed to break off when plants mature, resulting in tumbleweeds that can spread by wind as far as 1 kilometer or more, losing 80-90% of their weed seeds along the way and shedding up to 100,000 seeds plant as it rolls, most of which are viable. The faster it rolls the more seeds are dropped.
Kochia And Herbicide Resistance
- Most kochia is resistant to group 2 herbicides which were first reported in Canada in 1988 and are now widespread across Canada and the US. These group 2 resistant biotypes germinate at lower temperatures than susceptible plants.
- Kochia is genetically very diverse; there are over 100 mutations for resistance known for Group 2 herbicides with no growth penalty.
- Resistance to group 9 (glyphosate) herbicides was first reported in 2017, it is estimated that up to 50% of kochia in many areas of western Canada is now resistant to glyphosate.
- Recent reports indicate cases of kochia resistant to a group 4 herbicide (dicamba).
- Kochia is an outcrossing weed so resistance can be spread through pollen as well as seeds.
- The tumbleweed properties of kochia mean that one resistant plant can spread seed to multiple, distant fields in a single year.
What Can You Do To Manage Kochia
There is no silver bullet or magic wand to manage kochia. Growers need to consider using a systems approach, starting before seeding and continuing throughout the year.
Keep It Clean:
- Start with clean seed.
- Sanitize your fields.
- Don’t allow mature plants to remain standing (tumble weeds are mobile).
- Till, mow, burn, or otherwise remove patches.
- Clean field equipment between fields.
- Decontaminate equipment.
- Clean harvesting equipment before leaving area to prevent spread of seed across field or to neighboring field.
- Control plants on the entire farm (including roadsides and yard sites) by mowing or removing weeds before they can set seed.
Change Up Management Practices:
- Consider pre-seed tillage and/or herbicide applications (kochia is often the first to emerge)
- Rotate crops; don’t rule out perennial crops as they are strong competitors once established.
- Choose a crop that is a strong competitor AND one that will allow herbicide use to control kochia in-crop.
- Cereal and canola crops are stronger competitors than pulse crops.
- Scout fields before spraying to determine the extent of the problem.
- Maximize crop competitiveness using good agronomic practices:
- Use high quality seed and increase seeding rates
- Narrower row spacing
- Place fertilizer to benefit your crop
- Seed later for better crop competition
- Don’t panic. Herbicides will continue to be important in kochia management.
- Avoid cutting herbicide rates and water volumes, and follow best practices for optimum herbicide performance
- Spray during good weather conditions for best control. (warm, humid, low wind, appropriate speed is best)
- Strongly consider herbicide “layering” – using products that control kochia in pre-seed and following up with products that control kochia in-crop.
- If you notice kochia patches that are not being controlled, remove these weeds before they go to seed. Remember that “1 year seeding = 7 years weeding”
- Do not discount the value of tillage if needed. Consider tillage in place of herbicides for chem-fallow whenever possible. Remember that “weeds will not resist a cultivator on a hot day”.
Herbicides And Timing:
- Kochia is most competitive under poor growing conditions; therefore, it is important to control newly emerged plants as they are more susceptible when young.
- Use products or tank mixes with multi-mode of action, especially if you are using glyphosate.
- Consider pre-emergent products (Edge®) in canola or labelled pulse crops as they offer a different mode of action.
- there are good herbicide choices in cereals and canola, but no good options for pulse crops.
- Use herbicide combinations with multi-mode of action for the best control and reduced risk of herbicide resistance.
- Spray early; control is difficult with larger plants and/or poor growing conditions.
- Pre-harvest applications can act as a desiccant and prevent further seed production.
- Post-harvest applications can control any late season germinating weeds, as kochia is a summer annual and does not overwinter.
Cereal In-Crop Options:
Canola In-Crop Options
Pulse In-Crop Options
- There are no good in-crop options for pulses to control kochia.
- Growers should strongly consider a pre-seed application of the pulse pre-seed products mentioned above or a pre-emergent product such as Edge® that will provide control of kochia.