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Mike Koenigs
TOUGH LESSONS: Corteva’s Mike Koenigs was busy this year working with retail dealers and farmers to get the best weed control possible in a difficult year.

6 lessons about weed control learned in 2019

This specialist says some situations you saw this year can help you improve weed control next year.

Mike Koenigs says the issues many producers faced with weed control and other challenges in 2019 actually started 12 months ago, with the late, wet fall in 2018. “Most farmers who apply nitrogen in the fall for corn didn’t get it on, and many people who rely on fall burndown herbicide applications didn’t get those on either,” Koenigs says. “Problems were brewing for weed control and other crop issues even before the wet spring turned into extreme planting delays.”

Koenigs is a market development specialist for Corteva Agriscience in Illinois. He has lots of hands-on experience with both farmers and retail dealers. Here are six key lessons Koenigs gleaned from 2019 that should help farmers set up for better weed control in 2020:

1. Weed control starts in the fall. It may be another tough fall to make herbicide applications, but when they’re possible, they can make a big difference, Koenigs says. That’s especially true if you’re dealing with a tough weed such as glyphosate-resistant marestail. The best time to get a jump on it is often in the fall. Fall applications fit especially well in no-till acres if you’re not using cover crops.

2. Residual herbicides are a must in both corn and soybeans. With problem weeds such as waterhemp, putting a residual herbicide down early and then coming back with an overlapping residual herbicide added in a postemergence application makes lots of sense, Koenigs believes. He sees a growing need for these residual herbicides, and those who used them tended to see better weed control in 2019.

3. Choose herbicides with multiple modes of action. Paying attention to modes of action and applying herbicides of different families is a must, especially to slow development of resistance in weeds such as waterhemp, Koenigs says. For example, in Corteva’s lineup, both Resicore and SureStart, two residual herbicides for corn, contain three modes of action. If adding postemergence products, it’s possible to hit weeds with at least five modes of action in one season.

4. Stay flexible on how you use herbicides. Several herbicides can be used either as preemergence or postemergence products, Koenigs says. In a year with so much variability in weather, like 2019, it was helpful to have the flexibility to apply a product preemergence if it made sense in some situations, yet apply it as a postemergence herbicide in other situations.

5. Pay attention to weed size. Herbicides went on later than usual this year, and many times weeds were taller than one would like due to weather delays, Koenigs notes. Know what size of weeds are specified on various product labels, and do your best to stay within those guidelines, he advises. Some fast-growing weeds, such as Palmer amaranth and even waterhemp, can go from within label to off-labeled size in a matter of days, if not hours.

6. Keep herbicide rates high. Tight budgets might tempt you to trim rates, but it was the wrong move this year, Koenigs says. With tougher weeds, he doesn’t think it’s good advice in any year. Tough weeds demand labeled rates applied at the right size of weed for good control.

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