Nearly all food labels in Vermont are now required to disclose when products include genetically engineered ingredients. The requirement, passed two years ago, became effective on Friday. The rule is the first of its kind in the United States, and although it applies only within the tiny state, it is having national impact. Most major food and beverage companies have already added language to their labels to meet the new rule, rather than deal with the logistical hassle of having separate labels for different states. But not all the same products will definitely be on shelves. Vermont's law requires the labeling of most packaged grocery products as well as any whole fruits or vegetables produced with genetic engineering. That means virtually all products containing derivatives of crops like corn, soy, canola and sugar from sugar beets will need labels, as most of those crops in the United States are grown from genetically modified seeds. Vermont's law is careful, however, to exclude cheese, a big business in the state. The law also exempts meat from animals that have eaten feed made from genetically engineered grains. The labeling issue has generated heavy and frantic lobbying by the Grocery Manufacturers Association and the trade groups representing major commodity producers of crops like soy and corn, who have wanted a federal law that would prevent mandatory labels.