I believe in Diana Dyer's book she lists the food high and low in pesticides and tries to choose accordingly. Here is the list I have when choosing organic foods.
High in Pesticides - apples, bell peppers,celery,cherries,imported grapes, nectarines,peaches,pears,potatoes, red raspberries, spinach, strawberries
Low in pesticides -cruciferious (broccoli,cabbage etc), blueberries, onions, watermelons, plums, eggplant, kiwi,eggplant,grapefruit
I usually keep my list handy while at the grocery store.
Hope this help in choosing your produce.
Mary
here is Diana Dyer's web address
www.cancerrd.com