EPA announced decision after receiving new information from manufacturer Dow that the weedkiller, Enlist Duo, is probably more toxic to other plants than previously thought

The US Environmental Protection Agency has withdrawn its approval of a controversial new weedkiller to be used on GM corn and soybeans, according to a story by Associated Press.

The EPA announced the decision after receiving new information from manufacturer Dow AgroSciences that the weedkiller, Enlist Duo, is probably more toxic to other plants than previously thought.

It was originally approved a year ago and is designed to be used with new strains of GM corn and soybeans. The agency says it needs to study whether wider buffer zones will be required to protect non-target plants.

The EPA's move was welcomed by environmental and food safety groups that had sued to rescind approval of the potent new herbicide. But it is sure to create anxiety for the agriculture industry, since many weeds have become resistant to glyphosate, an herbicide commonly used on GM corn and soybeans. Enlist includes a combination of glyphosate and an updated version of another herbicide, 2,4-D.

"With this action, EPA confirms the toxic nature of this lethal cocktail of chemicals, and has stepped back from the brink," said Earthjustice Managing Attorney Paul Achitoff. "Glyphosate is a probable carcinogen and is wiping out the monarch butterfly, 2,4-D also causes serious human health effects, and the combination also threatens endangered wildlife. This must not, and will not, be how we grow our food."

Dow issued a statement calling for rapid resolution of the matter, citing "the pressing needs of US farmers for access to Enlist Duo to counter the rapidly increasing spread of resistant weeds" and predicting that "these new evaluations will result in a prompt resolution of all outstanding issues."

EPA's decision means that Enlist Duo, which is currently on the market, won't be in wide use for plantings next spring. EPA hasn't said whether farmers already in possession of the herbicide will be able to use it, and that could be a topic for future litigation, said Andrew Kimbrell of the Center for Food Safety.

Critics say they're concerned the increased use of 2,4-D could endanger public health and more study is needed. The USDA predicted that the use of 2,4-D could increase by 200-600% by the year 2020.

EPA had earlier said when approving the new weedkiller that agency officials had used "highly conservative and protective assumptions to evaluate human health and ecological risks”. The EPA said at the time that the herbicide met safety standards for the public, agricultural workers and endangered species.

Now, EPA says it has "has received new information from Dow AgroSciences - the registrant of Enlist Duo - that suggests two active ingredients could result in greater toxicity to non-target plants."