Updating the critical weed-free period in canola

Project Summary

Overview

Globally and in western Canada, weeds are the largest contributor to crop yield loss. Appropriate timing of weed management is critical to achieve full yield potential. The critical weed free period (CWFP) dictates how far into the growing season weed management is required to avoid unacceptable yield losses.

Current timing of weed management recommendations in canola are based on critical period of weed control research conducted two decades ago. Since then, advances in hybrid canola and other technologies have led to more vigorous cultivars with improved competitive ability with weeds. In addition, new soil residual herbicides and crop stand densities modify the critical weed free period weed management options in canola. Neither of these have been studied in canola.

Practices that increase the competitive ability of the crop or early interference form weeds are expected to shorten the CWFP in canola and therefore lead lower risk and input costs by reducing the number of herbicide applications needed to prevent canola yield loss from weeds. Reduced reliance on herbicides and increased competitive ability of the crop are the most critical components of weed management and contribute to delaying the selection for and assist with management of herbicide resistant weed biotypes.

This research project will define the CWFP in new hybrid canola cultivars and examine the addition of soil residual herbicides and among several canola stand densities. This research will contribute to more efficient and sustainable weed management practices by optimizing canola genetics, plant stand densities and herbicide programs.

Purpose

This project seeks to optimize weed management, herbicide use and herbicide stewardship for canola production in western Canada.

Direct financial benefits from this project will include yield maximization in canola due to optimized herbicide use patterns and limiting herbicide application to only those necessary. Fewer and more appropriate in-crop herbicide applications reduce the selection pressure for the development of herbicide resistant weeds and management practices that make crop more competitive with weeds such as appropriate stand densities further contribute to this by directly suppressing weeds and improving herbicide efficacy. Proactive management to herbicide resistance is critical to avoid serious loss of productivity and rising weed management costs.
The results from this research will augment herbicide labels which indicate when it is biologically safe to apply a herbicide. Herbicide labels, however, do not indicate when it is biologically necessary to apply herbicides or other weed management tools to prevent yield losses. Weed management thresholds and critical periods provide that information.

Objectives

The four main objectives of this research are:

(1) Update the critical weed free period (CWFP), in specific, the end of the critical period of weed control, in canola using modern canola hybrid genotypes.
(2) Determine the effect of target plant density affect the CWFP in canola at different locations in western Canada
(3) Determine how herbicide program affects in-crop herbicide needs and the CWFP at different locations in western Canada
(4) Collect data from sufficient locations and years to be able to make sound recommendations regarding the CWFP under the various scenarios.