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Soybean burn will show up if you try to knock down big weeds

Soybean burn will show up if you try to knock down big weeds
Trade-off between knocking down weeds and burning soybeans makes late spray decisions tough.

There are fields of soybeans in Indiana which have not been sprayed yet this year. That's a safe bet. Fortunately, that number is dwindling. But it may never get to zero. At some point it may be time to pull the plug on spraying.

Related: Soybean herbicide injury due to perfect storm

One farmer reports that some of his fields are clean enough and it's just now getting close to dry enough to spray for the first time since emergence. He applied residuals which did a good job for a long time. If he sprays, he has the expense of spraying plus beans knocked down by the sprayer which likely won't recover this late. He's edging toward leaving those fields alone.

Bean injury could be factor: Applying certain herbicides this late at high rates could result in soybean injury.

Then he has a couple fields where ragweed hasn't taken over, but there are more than he likes to see. He isn't sure if they are resistant to ALS or glyphosate. If he can get in this week, he's thinking about the highest rate of glyphosate possible, and giving it a shot.

Weed control experts point out that if he hasn't already applied any glyphosate this year, then he can apply more than he might if he was planning two applications in a planned program. There is a maximum amount specified on labels that can be applied on the crop in any one season.

The other option is to opt for a more traditional burndown material, such as Cobra, specialists say. Going with ALS products probably isn't the best move since the farmer doesn't know if the weeds are ALS resistant or not, and they are already big.

The next choice is Cobra at full rate or a reduced rate. Full-rate would work best on the weeds but would likely produce plant injury in some cases. Plant injury this late in this kind of season isn't a great idea either. If you're going to use it this late, go with a reduced rate, weed control specialists say.

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