Keep Kochia Seed Production to a Minimum
By Mitchell Japp, MSc, PAg
Kochia has become one of the most problematic weeds in modern production systems. Although it is not very competitive, it is a prolific seed producer and adapts well where competition is lacking, such as in dry or saline soils. Additionally, kochia is becoming resistant to several different herbicide modes of action. It is also able to adapt and produce seed at various times of the year. Because it is such a prolific seed producer, managing kochia is important throughout the year.
Kochia seeds have a short longevity in the environment, lasting only one to two years. Pre-harvest weed control can be an option to help reduce seed production from kochia. Malt barley buyers are not willing to accept barley treated with pre-harvest weed control products. Fortunately, barley is a competitive crop, so early weed control can keep kochia seed production to a minimum during the growing season. Kochia that is growing in a competitive crop like barley will produce fewer seeds.
Barley is typically harvested early compared to other crops, especially early in hot, dry conditions, as many areas have experienced in 2023. When crops are harvested mid-August or earlier, a single kochia plant can still produce on average 4,100 seeds prior to the first killing frost1. This research is based in Montana, where the growing season can be a little longer than on the Canadian prairies, but Dr. Charles Geddes with Agriculture and Agri-Food Canada at Lethbridge has seen similar results in his research. Controlling those late-season kochia plants can make a difference to the weed pressure for next year.
This year in particular, harvest is ahead of normal progression. Kochia is well-adapted to dry conditions and is likely growing in fields that have been harvested. A post-harvest herbicide may be warranted to reduce kochia seed production in fields harvested before mid-August. Fields harvested after mid-August are not expected to have enough time for kochia plants to produce seed. Although, a post-harvest herbicide may be warranted for moisture and nutrient management.
- Postharvest Kochia (Kochia scoparia) Management with Herbicides in Small Grains. Mickelson et al. 2017
- Herbicide Resistant Kochia – Challenges and Management. The Growing Point Podcast
- The Kochia Conundrum. Agronomist Happy Hour podcast
- Wheat School: Cultural practices as effective as a new mode of action
- Controlling the Weed Seedbank