WASHINGTON, D.C. — The USDA has released statements detailing the potential impact to the environment of genetically engineered (GE) plants resistant to the herbicides 2,4-D and dicamba.

The agency’s Animal and Plant Health Inspection Service (APHIS) issued its final Environmental Impact Statement (EIS) on Dow AgroSciences’ Enlist plants Aug. 6. Also released last week was a draft EIS on Monsanto Co.’s GE plants resistant to dicamba.

Dow had sought deregulation of three GE plants – Enlist corn, Enlist soybeans and Enlist 3 soybeans – developed to be resistant to 2,4-D. In its final EIS, APHIS said its preferred alternative is to fully deregulate the three plants.

The action is "consistent with APHIS’ final plant pest risk assessment that found 2,4-D resistant corn and soybeans are unlikely to pose a plant pest risk to agricultural crops or other plants in the United States."

The final EIS was expected to be published in the Federal Register Aug. 8. After a 30-day comment period, APHIS will make a final decision on deregulation.

The U.S. EPA is also reviewing the use of 2,4-D and is assessing the potential for environmental and human risks associated with its use, APHIS said. In May, the EPA released a draft proposal to register Enlist Duo, which contains glyphosate and the choline salt of 2,4-D. Choline salt isn’t currently registered for use in controlling weeds in GE corn and soybeans, the EPA has said. The salt in 2,4-D is less prone to drift and volatilization than its other forms, according to the agency. The EPA has said it expects to make a decision on registering Enlist Duo by late summer or early fall.

The release of the USDA’s impact statement brings American farmers one step closer to obtaining a critical tool needed to manage resistant and hard-to-control weeds, according to a statement from Indianapolis, Ind.-based Dow.

"This has been one of the most extensive evaluations of a new agriculture technology in recent history," said John Cuffe, global regulatory sciences and regulatory affairs leader for Dow.

"USDA has produced a thorough, modern assessment. Now we are eagerly anticipating final regulatory approvals from USDA and EPA so farmers can get the help they need."

The USDA’s statement did offer a note of caution in regard to longer-term use of 2,4-D, saying with deregulation it expects to see increased usage of the herbicide over a wider part of the growing season. The change in management practices expected with that usage may increase the pressure for selection of 2,4-D resistant weeds, the statement said. "Growers themselves can influence this selection pressure by the management practices they choose," APHIS noted. "Some examples of practices that can be followed to reduce or delay the selection of herbicide-resistant weeds include rotating crops, rotating types of herbicides, using cover crops, scouting for weeds and using mechanical tillage to prevent weeds from flowering."

The number of farmers who may opt to use best management practices is unknown, the agency said, making it difficult to "predict when and the extent to which 2,4-D-resistant weeds will become a problem."

The Save Our Crops Coalition (SOCC) petitioned the USDA in April 2012 for an EIS on 2,4-D and dicamba. The request was granted in May 2013. "Everything is going as we like on that whole deal (regarding the Dow-related EIS)," said Steve Smith, SOCC chair. "There was nothing surprising in the final EIS."

The SOCC was formed in 2012 over concerns with off-target damage from exposure to 2,4-D and dicamba. A primary concern of the SOCC has been the tendency for synthetic auxins to volatilize or for their active ingredients to evaporate. The active ingredients could travel 1-2 miles from their intended target, Smith has said.

In its draft EIS on Monsanto’s GE plants, APHIS said its preferred alternative is to deregulate the varieties. The agency said its initial plant pest risk assessment found GE cotton and soybeans are not likely to pose a plant pest risk to agricultural crops or other plants. Once the draft statement is published in the Federal Register, a 45-day comment period will begin.

The announcement regarding Monsan-to’s GE plants – Roundup Ready 2 Xtend soybeans and Bollgard II XtendFlex cotton – is a sign of progress, a company representative said in a statement.

"This is good news for America’s farmers," said Michelle Vigna, Monsanto launch manager for the Roundup Ready Xtend crop system. "It is an important step in the regulatory process and we are encouraging farmers to urge APHIS to complete this action as soon as possible to ensure that U.S. soybean and cotton farmers can gain access to these important new technologies."

Smith, also director of agriculture with Elwood, Ind.-based Red Gold, said Monsanto’s compound is very volatile. He said he would be urging SOCC members and farmers to voice their opinions during the comment period. "I didn’t expect the draft EIS this soon," Smith said. "I really thought it might take a little longer. It came out two to three months earlier than expected."

As with 2,4-D, the EPA is also conducting a risk assessment of the proposed new uses of dicamba, including any potential harm to human health and the environment. The EPA reviews of 2,4-D and dicamba were also initiated by a request from the SOCC.