Many fruits and vegetables found in supermarkets and other food stores have stickers attached with numbers. These numbers are the Price Look Up (PLU) codes, an aid so those working at checkout don't need to remember every item of available produce.
Four-digit numbers starting with a "3" or "4"—such as the mangoes in the photo above—represent conventional fruits and vegetables sprayed with pesticides. (Click on photo for detail.)
Five-digit numbers starting with a "9"—as seen on the mango below—mean the produce has been grown organically. (The four-digit number simply is preceded with a "9.")
In addition, five-digit numbers starting with an "8" have been reserved for genetically engineered (GE) fruits and vegetables, but you will never see these stickers. First, only a handful of items—papayas from Hawaii, some yellow and green summer squash, and some corn on the cob—are grown this way. Second, retailers don't want people to know what is genetically engineered.
Know that over 90 percent of the corn and soy grown in the United States is genetically engineered, so assume that any non-organic packaged or processed food contains GE ingredients, since corn and soy are essential building blocks of these foodstuffs. (Read the ingredients on ketchup, energy bars and breakfast cereals and you'll see what I mean.)