Soybean Field bordering my acreage at the house here in Baldwin county has been sprayed with Roundup 3x. Uncertain which pigweed it is, but pretty certain it is the spiny variety, is now about a foot taller than the mid thigh high beans. It is the only weed in the field. The 3rd spraying did little more than wilt the plants for about a week.
The farmer we lease from in the MS Delta told us in casual conversation that Dicamba had some serious issues with both resistance and drift. He was way more concerned with drift. A farmer can be responsible and spray under the best circumstances he said and 2-3 days later the chemical volatilizes and drifts to the neighbor. And as he said...it ain't good for neighborly relations.