You can read the label for Authority herbicide from FMC all day, soaking in every word of the fine print. Unless we've been grossly misinformed, you won't find wording that says you can't mix Authority with Sharpen, a product from BASF, in the same tank mix. However, if you read the label for Sharpen, you will find a statement telling you not to use Sharpen with Authority.
What gives? Bill Johnson, Purdue University Extension weed control specialist, says it's not that unusual in the modern, competitive, chemical world to find those kinds of situations out there. His best advice is to read the label of each product before you mix them, even if you've done it without incident for the past several years, and even if your dealer says "everybody else is doing it."
You owe it to yourself to know what risks you're taking, and determine if you are willing to take that risk, he says.
On the hook for crop damage
What risk are you taking if you mix two products, and one label for one product says one thing, while the other label says something different, or doesn't say anything?
From a legal standpoint, Johnson says that the product with the most restrictive label is the one that will be followed if something goes wrong and you're seeking adjustments.
"What we've seen is that in cases like this, the product with the most restrictive label prevails," he says. In other words, if one label says don't' use A with B, but B doesn't say you can't use it with A, and you use A with B and have a problem, you're on your own from a legal standpoint.
The ruling would be that you didn't follow all label directions. The best advice is to follow the label that is most restrictive. If you're confused, consult with your chemical dealer, company rep or an Extension educator, he advises.
Continued reading: Know herbicide mode of action and control resistant weeds with online tool