Plan for fall weed control as part of your post-harvest workload

Canada thistle.

It’s spring and, as usual, time is tight before seeding. Everyone knows how beneficial pre-seed applications can be for top-yielding crops by eliminating early weed competition and saving moisture and nutrients for vigorous seedling development. But, how can you benefit from early-spring weed control when there’s never enough time? One option is to start even earlier. Right back to the fall.

Post-harvest weed control, or fall pre-seed, offers the benefits of spring pre-seed with the added workload and time management payback you gain in the spring.

Several products are registered for fall pre-seed weed control that, tank mixed with glyphosate, cover a wide spectrum of weeds. Most important in fall are winter annuals and dandelion. Canada thistle shouldn’t be ignored either. Winter annuals left unchecked reduce soil moisture and nutrients throughout fall and in the spring, when they resume growth. Dandelion, with its large root system, is difficult to control; however, research has shown that fall is the best time to tackle this persistent weed. Cooler conditions lead the plant to translocate energy to the roots, carrying the herbicide along and increasing the likelihood of complete control.

Once the soil cools in the fall ( ≤ 10 C), certain products offer control that extends to spring. The breakdown of the active is halted over the winter, and early-emerging, susceptible weeds are controlled when activity restarts in spring. This is especially important for volunteer canola, which emerges in flushes in fall and spring and can be high in numbers.

Generally, fall pre-seed sets you up for spring. Additional control may be required due to high weed populations, delayed seeding or the effectiveness of the chosen product.

Bottom line, plan ahead for fall weed control as part of your post-harvest workload. You will thank yourself come spring and your crops may deliver bigger results.

Kelly Bennett is the category leader for herbicides in Western Canada at Corteva Agriscience.

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