Early Season Weed Control in Canola
Updated: May 26, 2020
Research has shown that one weed emerging with the crop has the same effect on yield as 100 weeds emerging 3 weeks later. Pre-seed/pre-emergent and early season weed control is important for maximizing yield.
Pre-Seed Weed Control
It is best to control perennial and winter annual weeds prior to seeding, as harrowing and seeding cause the weeds to become broken up and covered in dirt, lowering the herbicide’s efficacy (see Figure 1).
Some perennial and winter annual weeds have allelopathic properties, and furthermore, also compete for moisture, sunlight, and nutrients.
Most perennial and winter annuals can be controlled with a glyphosate application from 1-2 REC/ac, depending on the weed and size. If cotyledon stage annuals are all that is present in a field, the disturbance from harrowing and seeding can often provide enough control and these fields can be watched for pre-emergent spray.
Figure 1. Harrowing before spraying perennials decreases herbicide efficacy.
Pre-Emergent Weed Control
When checking canola for weeds pre-emergent spray timing, it is important to consider which weeds are emerging and which canola system you are using. For example: Liberty has poor control on cleavers and hemp nettle and if these weeds are present prior to the crop emerging, an application of light rate glyphosate could be warranted.
In glyphosate tolerant systems, pay attention to annuals like wild buckwheat and consider their size. Glyphosate does poorly on buckwheat larger than 2-3 leaf, so controlling it early is important.
Products for Specific Weed Problems
Conquer: group 6 bromoxynil and 14 pyraflufenethyl, pre-seed/pre-emergent for control of RR canola and as a resistant management tool for kochia.
Command: Group 13 clomazone, pre-seed for residual control of cleavers, no contact properties only treats the soil, up to 3 weeks residual control.
Facet L: Group 4 and 26 quinclorac, pre-seed/pre-emergent at 40ac/jug for up to 3 weeks residual control on cleavers or in crop at 80ac/jug for control of cleavers; gearing towards LL tolerant and Clearfield canola systems. Can be tank-mixed with Liberty, glyphosate and Ares. Re-cropping restrictions: 10 months after application, peas can be grown, 12 months for oats, 22 months for flax, lentils and soybeans. Caution should be taken with fababeans.
Controlling weeds pre-seed and prior to emergence is the best way to kick start your crop. Consider strategies like spraying pre-seed for winter annuals and perennials, or pre-emergent for annuals that are getting too big. There are a number of products registered that can help tackle problem weeds.
Let us take care of weed control: email firstname.lastname@example.org to inquire about agronomy services or read more here.
Olivia Stephanyshen, CCA-PP