The company in July notified the US regulatory body that it had discovered trace amounts of an unapproved GM rice in samples of commercial rice seed.
But although the USDA announced in August that a scientific review of available data revealed no human health, food safety or environmental concerns were associated with this rice, the GM contamination has sparked a flow of reactions against the firm and the US rice export market.
The European Commission has adopted a decision requiring imports of long grain rice from the US to be certified as free from the unauthorised GMO LL Rice 601. The Food safety Authority of Ireland has implemented a ban on uncertified US long grain rice products, and the UK's Food Standard's Agency has also now put into effect tough measures to ensure that the UK's food chain remains free from unauthorised GMOs.
Such limits on rice imports have had an immediate impact on US farmers. Attorneys for some rice farmers have sued Bayer CropScience, alleging its GM rice has contaminated the crop.
A lawsuit filed in the US District Court for the Eastern District of Arkansas in Little Rock, alleges that a unit of Germany's Bayer corporation failed to prevent its GM rice from entering the food chain. Strict limits placed on US rice imports have led to a dramatic fall in the price of US rice.
"Our clients feel that Bayer should have taken stricter steps when growing this genetically modified rice to prevent it from contaminating the commercial rice market," said Richard S. Lewis, a partner and environmental legal expert with the Cohen, Milstein law firm.
"Bayer's actions have resulted in an unprecedented price drop financially impacting all rice farmers."
LL Rice 601 is one of a number of GM rice lines developed by the biotech company Bayer. Marketed under the brand name LibertyLink, these were engineered to tolerate the herbicide glufosinate ammonium. They include two lines of genetically engineered (GE) rice with the same herbicide-tolerant protein, which were approved in 1999.
But LL Rice 601 has not undergone the necessary regulatory process for USDA to determine that it can be safely produced commercially. It is therefore known as a "regulated" crop.
According to the USDA, Bayer had no plans to market the GE rice variety, which is why it had not requested "deregulation" - or approval.
However, the consequences of the recent contamination have now prompted Bayer to petition for the deregulation of LL Rice 601. The USDA has said that the petition is in accordance with its Animal and Plant Health Inspection Service (APHIS) regulations concerning the introduction of GE organisms and products.
The petition is open to public comment until October 10.