* Dow's Enlist corn delayed likely until 2015 * Monsanto, Dow say cooperating with USDA * Critics applaud USDA move May 10 (Reuters) - The U.S. Department of Agriculture said Friday it will extend its scrutiny of controversial proposed biotech crops developed by Dow AgroSciences, a unit of Dow Chemical, and Monsanto Co. after receiving an onslaught of opposition to the companies' plans. USDA said it will conduct two separate environmental impact statements "to better inform decision-making" on the approvals sought by Dow and Monsanto. The news frustrated Dow officials who had hoped to have secured regulatory approval and have their new herbicide-tolerant corn called "Enlist" on the market by 2013 or 2014 at the latest. But 2015 is now likely the best hope for commercialization, said Dow AgroSciences spokeswoman Kenda Resler Friend. "They (regulators) have had a long time to look at the information," said Friend. "This is something that farmers are going to lose from." But critics applauded the move. Many have warned that both the new crops planned by Dow and Monsanto, and the new herbicide use tied to the crops, will cause a range of problems for farmers and rural communities. "USDA is taking the issue...seriously," said Paul Towers, a spokesman for the Pesticide Action Network. "We're hoping that a thorough review... will ultimately result in denials." Monsanto issued a statement calling the development "unexpected," and saying it would cooperate with the government in the assessment. The company said farmers need its new technology to maximize crop production. Dow AgroSciences is hit the hardest by the USDA decision as it had hoped to have approval by now, while Monsanto has been aiming for "the middle of the decade." Dow wants to roll out Enlist corn, and then soybeans and cotton to be used in combination with its new Enlist herbicide that combines the weed-killers 2,4-D and glyphosate. The Enlist crops are genetically altered to tolerate treatments of the Enlist herbicide mixture. Dow says Enlist will help combat an explosion of crop-choking weeds around the United States that have become resistant to glyphosate, which is the chief ingredient in the popular Roundup herbicide. Likewise, Monsanto, in conjunction with BASF, want regulatory approval for new genetically altered soybeans and cotton that resist a new dicamba-based herbicide. Both the Enlist system and the dicamba system are seen as replacements for the combination of Roundup herbicide used on Roundup-resistant crops that now dominates U.S. agriculture. The USDA has received thousands of comments on both of the new cropping systems that laid out a variety of concerns. In addition to increasing weed resistance, many farmers fear increased use of the new herbicides that would come with the new crops would cause damage to fruits, vegetables and other crops as dicamba and 2,4-D have been known to travel on the wind far from the fields where they are sprayed. Many also worry that the new biotech crops will contaminate conventional and organic crops. And Dow's Enlist herbicide is also controversial because 2,4-D, or 2,4-Dichlorophenoxyacetic acid, was one of the ingredients in Agent Orange, the Vietnam War defoliant that was blamed for numerous health problems suffered during and after the war. Although the main health effects of Agent Orange were blamed on the other component of the mixture (2,4,5-T) and dioxin contamination, critics say 2,4-D has significant health risks of its own. The Center for Food Safety had threatened to sue the government if it approved Enlist. Center for Food Safety attorney Andrew Kimbrell said he thought the USDA had little choice but to conduct environmental impact statements given USDA has lost court challenges to its approvals for biotech sugarbeets and alfalfa for failing to conduct such assessments for those crops. "I think they were between a rock and a hard place," Kimbrell said of USDA. "They were going to be forced to do this anyway. The rush to judgment here has been halted."