A coalition of enviro groups yesterday petitioned the Agriculture Department to tighten its regulation of genetically engineered crops, accusing the department of approving new biotech plants without requiring adequate tests to assure that they won’t harm the environment. Plants that are artificially engineered to be resistant to pests could pass along resistance genes to weeds or reduce the genetic diversity of existing crop varieties, argued the coalition, which includes the Sierra Club, the Natural Resources Defense Council, and the Union of Concerned Scientists. A number of enviro and consumer groups are also campaigning for mandatory labeling of genetically modified foods, arguing that citizens should know what they are eating. Consumers Union, publisher of Consumer Reports magazine, explains in Grist why people should be cautious about GM foods.