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Don’t Change Your Preemergence Weed Management Plans

June 4, 2019
This agronomic image shows lambsquarter


Given the late start to planting this year and that some parts of the Midwest still haven’t been able to plant, it may seem more efficient to skip a preemergence herbicide. Skipping early-season weed control could give tough-to-control weeds a leg up in your field, ultimately allowing them to compete with your crops for water, sunlight and important nutrients.

Preemergence herbicides are a critical component of a weed management strategy, and are important in helping to fight resistance development.

Preemergence applications not only limit the summer annuals that do come up, but they are also effective at lowering the weed seed bank from any winter weeds that went to seed. It’s an important application for starting clean as planting continues, and staying clean through the summer and into harvest.

Many of the common summer annuals that growers fight each year are expected to be a problem again this season. As the University of Illinois Extension & Outreach notes, experts have already seen flushes of weeds such as giant ragweed, waterhemp and lambsquarters. In places where planting hasn’t begun, these weeds have no competition.

The best course of action for both corn and soybean growers is to simply stick with the plan. Overlap residual preemergence and post-emergence herbicides with multiple effective sites of action. This kind of program should help prevent weeds from breaking through applications.

It’s also critical to use full labeled herbicide rates, and, especially for areas where weeds are already emerging, knock out weeds before they reach 4” tall. Herbicide resistance continues to be a primary concern, and using half or cut rates – or applying herbicides to weeds that are already too tall – may not kill the weed. If a damaged weed is able to regain strength, it may do so with a new resistance to the herbicide application.

Visit ResistanceFighter.com to learn more about these and other techniques for managing tough and resistant weeds.

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