Young says early resistance problems can be difficult to spot, or are reasoned away by producers. “If a producer sees a slight failure rate, he may blame it on a faulty nozzle, poor herbicide coverage, or bad weather — anything but resistance. If those few plants go to seed, the next year you will have an even greater problem. The weeds will still be there, and as long as you keep using the same chemistry, you will continue to select for that weed.”

Weed resistance is a numbers game, says Les Glasgow, technical asset lead and head of weed-management strategies for Syngenta. “Weed resistance is all about how many weeds are being exposed to a single mode of action,” he says. “That sets you up for resistance.

“It doesn’t matter if the active ingredient is glyphosate, atrazine, or any of the other chemistries,” Glasgow continues. “If you overuse it, the plant will develop resistance.”