No. 1 Spring Weed Concern

Posted March 17, 2020 | By: Gary Topham

Manager of Agronomic Services with Nutrien Ag Solutions in Manitoba.

While resistant kochia and wild oats may be concerns, the No. 1 weed issue this spring, in many areas, could be volunteer canola.

The Canola Council of Canada has demonstrated under “normal” harvest conditions, and with a properly set combine, farmers lose one to two bushels of canola seed.

For many farmers the 2019 canola harvest was not normal, and many fields had to be harvested weeks after full maturity. Even if the canola was a pod shatter, harvest management variety, there was most likely extra yield losses.

When we determine how many seeds in a bushel (about 4.25 million seeds) and how many square feet in an acre (43,560), we find a one-bushel loss equates to about 100 volunteer canola seeds per square foot. A two-bushel loss at harvest equals 200 volunteer canola seeds per square foot.

Typically, we would see a large percentage of volunteer canola germinate in the fall and be killed by frosts. Because of the late harvest, combined with declining fall soil temperatures, less volunteer canola germinated and was killed off last fall. This means there will be a significant number of volunteer canola that will germinate this spring. I would estimate upwards of 50 volunteer canola per square foot.

The past two springs have been cooler than normal and the current forecast for 2020 is the same. In these conditions, most of the cereal crops are seeded before the volunteer canola emerges.

There is no right or wrong approach on how to control your volunteer canola but now is the time to start thinking about a pre-seed, post-seed pre-emerge, and in-crop options that work for your farm management practices.


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