By Harry Brook
Kochia used to be a plant associated with the southern parts of the province. However, over the years, this weed has continued to spread and is becoming a serious problem in Central Alberta. Kochia is very salt-tolerant and starts to grow in those areas where salinity prevents many other plants from growing. From there it spreads to the rest of the field and can seriously affect the crop yield. It has further competitive advantages, such as a tap root that can go down 10 feet to access moisture and nutrients, and can grow up to 6 feet tall, competing with cereals and corn.
In previous years, research was conducted on using kochia as a forage crop for livestock. It does contain high protein and decent energy. However, it also contains some substances that negatively affect cattle. If cut at a more mature state, kochia should not be used at more than 40% the total diet of a beef cow ration. If the kochia is less mature, the safe level is no more than 30% of the total ration. Due to high oxalate content in kochia, too much can interfere with calcium levels in the blood, reducing them to dangerously low amounts. This can be compensated through using more calcium supplementation in the minerals provided to the cattle.
Kochia is a very prolific seed producer and, once the plant is mature, the stem breaks off from the root and spreads seed as it tumbles in the wind. One plant can produce up to 25,000 seeds. The tumbling nature of the plant also aids in seed dispersal over distant areas. You could say it is well travelled. Because it both self-pollinates and cross-pollinates, each kochia seed is a unique genetic package with very diverse genetics in each seed, which can quickly lead to herbicide resistance.
When it comes to control, kochia is not that easy to kill. A lot of popular broadleaf herbicides are group 2 or use group 2 products. If you have kochia in your field, assume it is group 2-resistant. Glyphosate-resistant canola is a great cleanup crop, but there are already significant stands of kochia in the county resistant to glyphosate. Kochia resistant to group 4 herbicides (phenoxy’s, 2,4-D, fluroxypyr) is also found, in spots, in the county. The real problem is that there are populations with multiple mode of action resistance. You can start running out of herbicide products to use.
In certain crops, it is difficult to find herbicides that will work on kochia, such as in flax or pulses. These crops rely heavily on group 2 herbicides. If you have these crops and kochia is an issue, you may have to resort to old chemistry such as a soil applied, pre-emergent, granular product, in the fall.
There are a lot of kochia patches around the countryside this year, usually growing in the saline patches in the field. However, there are other patches growing with the crop. If you wish to test for herbicide resistance, you can send a seed sample away to the Saskatchewan Crop Protection Laboratory in Regina but resistance testing is NOT cheap!
Another approach is to apply some limited cultivation to patches as it can be controlled with tillage. Kochia is an extremely difficult weed to keep under control. The one saving grace is that the seed does not remain viable for long in the soil. Putting land into a perennial crop such as hay or pasture can quickly reduce the weed seed bank. Keep an eye on this weed, it’s everyone’s problem.