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Resistant or tolerant weeds?

An agronomist with Winfield suggests some herbicide-resistant weeds aren’t actually resistant, just tolerant.

Mark Glady says either way it’s important to spray weeds when they’re small.

“You can have a tolerant waterhemp, that if it gets up to six or eight inches tall, we probably can’t kill it with RoundUp or other tank-mix partners.  But if you can spray that waterhemp at two inches, and we saw this a lot last year (in west central Minnesota), guys got out early at two inch waterhemp or less, and did a very good job controlling them with glyphosate and a tank-mix partner.”

Glady tells Brownfield another key is using the right adjuvant.

“A lot of times just going out and spraying the herbicide isn’t enough because if we’re spraying a post-emergence herbicides, more than likely we’re using water as our carrier.  When individual water-based spray droplets land on a plant’s leaf, a waterhemp or lambsquarters leaf, all plant leaves have wax in them.”

He says wax is an oil and water and oil don’t mix well.  In his opinion, getting the spray droplets into the plant is the most difficult part of killing a weed.