Chemical weed control in canola

Canola is an important break and cash crop in Western Australia. To provide maximum benefit to the following crop, while maximising the yield potential of canola, growers should aim to control weeds as early as possible. There is a wide suite of chemicals available for use before sowing, before crop emergence, in-crop and near maturity, which along with cultural techniques provide opportunities for effective weed control in canola.

Managing summer weeds is important to avoid seeding delays, conserve nutrients and moisture for the canola crop to use during the growing season, and minimise potential green bridge and allelopathic impacts.

Strategies for controlling emerged weeds (before sowing canola) using knockdown herbicides are similar to those for most other crops. However, due to the common practice of sowing canola early (April) in many regions, there is often a limited emergence of winter weeds before sowing canola which places heavy reliance on in-crop or residual weed control options.

Ideally, canola should not be sown into paddocks with a high weed burden. Delayed sowing of early maturing canola varieties, particularly if conventional canola is being grown, is a better option for achieving effective knockdown weed control in very weedy paddocks. This may only
be practical in high rainfall, long growing-season regions unless a very early maturing variety is available. If seasonal conditions permit, growers should use a double knock whereby two sequential but different weed management tactics are applied.

Herbicide information is regularly updated, therefore we advise reading herbicide labels for rates, tank-mixing compatibilities, crop and weed growth stages, requirements for adjuvants, plant and environmental conditions, rain-fastness and withholding periods.

The purpose of this bulletin is to provide a handy reference on herbicide options registered for different canola herbicide tolerance systems. Growers should engage their consultant to determine the herbicide tolerance system that meets their specific circumstances - taking into consideration the weeds present and their herbicide resistance status as well as the crop rotations and economic and weed management goals of the farming system.