Agronomy •  2020-04-07

Pre-seed weed control is important this spring

By Kelly Bennett and Rory Degenhardt 
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Kelly Bennett is the category leader for herbicides in Western Canada and Rory Degenhardt is the integrated field sciences research leader for Canada at Corteva Agriscience. Both are based in Alberta.

Published by Grainews Magazine April 7,2020 edition: Weed control will be a different challenge this year. With little fall weed control and good moisture, fields will have an abundance of overwintered annuals, such as cleavers, flixweed, narrow-leaved hawk’s beard and volunteer canola, alongside spring emergence of other annual and perennial weeds. These overwintered annuals are a particular challenge as they are often large and hardened with thick cuticles making them hard to control. They also consume significant moisture and nutrients. 

This spring, pre-seed weed control is especially important for starting crops off right and maximizing yield potential. However, due to weed density and diversity, high-performing combinations with glyphosate will ensure control of all weeds present, while also delaying the onset of glyphosate- resistant weeds.

For farmers with harvest to complete, planning ahead or utilizing custom spraying will be important to ensure pre-seed weed control is feasible. Products offering a period of extended control will be preferred for preparing fields to seed cereal crops to manage the higher potential pressure of flushing volunteer canola. If time is short, prioritize the fields with the most weeds first.

Better moisture conditions should lead to more routine incrop weed control in 2020. Lower wild oat pressure in 2019 led to more use of lower-cost, lower-performing graminicides. Despite smaller populations, escapes were allowed to go to seed. Higher-performing products will provide better results, especially with the higher wild oat populations expected in 2020. Broadleaf weed populations are also expected to increase. Scouting for size, density and numbers of species will be important to ensure the right product is chosen.

Herbicides play a critical role in weed control, but it is important to remember that practising multiple strategies leads to the best results. Good agronomic practices that lead to a denser crop stand will ensure partially controlled or subsequent flushes of weeds are suppressed, making your overall weed control program more effective.