Farmers in the United States are heading for a crisis as weeds resistant to glyphosate grow in the majority of soy, cotton and corn fields - and the chemical industry has no answers.

That's the message from an important article from Science journal. The article is behind a paywall, but we've summarised it below.

Contrary to pro-GM trolls' constant messaging online that glyphosate resistance is a problem not of GM but of bad farm management (yes, once again farmers are to blame for using GM technology exactly as prescribed by GM seed companies), the article fingers the spread of GM glyphosate-tolerant crops as the undoubted culprit.
What happens when weed killers stop killing?
Robert F. Service
Science vol 341, 20 Sept 2013
[article behind paywall; summary below by GMWatch]

US farmers are heading for a crisis, says Stephen Powles of the University of Western Australia. Weeds resistant to glyphosate - the world's most popular herbicide - are now present in the vast majority of soy, cotton, and corn farms in some states. Even worse, weeds that can shrug off multiple other herbicides are on the rise. Chemical companies have little to offer: Few new weed killers are near commercialization, and none with a novel mode of action for which there is no resistance.

Herbicide resistance has ebbed and flowed for decades. But because most herbicides could not kill all weeds, farmers had to continually rotate crops and herbicides to prevent resistant weeds from taking over their fields. That picture changed in the 1990s with the commercialization of transgenic crops resistant to glyphosate, marketed as Roundup. The use of glyphosate soared. But the overuse had a cost, selecting for resistant weeds.

GM seed companies are developing new seed varieties resistant to herbicides other than glyphosate, to enable farmers to use alternative weedkillers. Although weeds have already evolved resistance to those herbicides, Powles says the new seed-and-herbicide combos should work if used with proper crop and herbicide rotation. However, he adds, if there is an over-reliance on them, they will fail rapidly.

If that happens, farmers may have little to fall back on. No new herbicide with a novel mode of action has hit the market in 20 years. And researchers at an American Chemical Society meeting meeting say they know of no new herbicides on the way that are effective, short-lived, and nontoxic to other life forms. Growers think there will be something over the horizon that will bail them out, says Larry Steckel, weed management scientist at the University of Tennessee's West Tennessee Research and Education Center in Jackson. But there isn't.