Thanks to Food Democracy for this handy tip:
The product look-up code (PLU) is a 4 or 5 digit code on items sold loose or by bunch, by weight or by each. Most non-prebagged produce in the supermarket is sold this way. The program is voluntary, but if a shipper is using the system, you can determine whether an item is genetically modified or organic from the PLU.
- Conventionally grown food (not genetically modified, not organic) will have a 4 digit PLU.
- Organic food will have 5 digits starting with a 9, e.g. an organically grown banana would be 94011.
- Genetically modified food will have 5 digits starting with an 8, e.g. a genetically engineered vine ripe tomato would be 84805.
Again, this system is voluntary. No shipper is required to use it, and the fact that there's no "8" prefix on a PLU doesn't guarantee it's not a genetically modified product. Ask your supermarket manager to find out for you whether their shipper is using the 8 prefix for genetically modified foods.
Or better yet, buy your produce directly from the farmer.