A federal judge on Friday banned the planting of genetically modified sugar beets engineered by Monsanto Co in a ruling that marks a major setback for the biotech giant. US District Judge Jeffrey White ruled in 2009 that the US Department of Agriculture had approved Monsanto's genetically modified sugar beets without adequate environmental study. Sugar beets account for over half of the nation's sugar supply. But conventional sugar beet seeds remain widely available and environmentalists filing suit said the judge's decision should not significantly affect sugar production. White's decision on Friday to impose the ban did not apply to crops already planted or harvested. It stems from a lawsuit brought by environmentalists over Monsanto sugar beets engineered to be resistant to the weed-killer Roundup. Roundup is also manufactured by Monsanto and was sold to farmers together with the genetically altered sugar beet seeds. Environmentalists have argued that the “Roundup Ready” crops have increased the use of herbicides and herbicide- resistant weeds. Monsanto has claimed in court papers that revoking the government's approval of its genetically modified seed could cost the company and its customers some $2 billion in 2011 and 2012. Agriculture Department spokesperson Caleb Weaver said the USDA was reviewing the judge's order “to determine appropriate next steps.” A Monsanto representative referred reporters to Duane Grant, an Idaho sugar beet farmer and chairman of the Snake River Sugar cooperative. “Before planting next spring's 2011 crop, clearly we are going to have to understand all of the implications of the judge's ruling, and what might be open to us,” Grant said. Sugar beets make up a little over half of the US sugar crop, and 95 percent of sugar beets come from Roundup ready seed, Grant said. The Center for Food Safety has countered that farmers can easily go back to using conventional sugar beet seeds, which were widely used as recently as two years ago. Most US sugar beets are planted in March, April and May, he said. The government has valued the sugar beet crop, which is largely grown in 11 states, the bulk of them in the Midwest, at $1.335 billion for 2007