Groups like Consumers Union and the Environmental Working Group have used sophisticated computer analyses to estimate how often which fruits carry residues of the least and most dangerous pesticides. Using their data, we've boiled it down to one simple rule: Try to buy organic apples, cherries, grapes, peaches, pears, raspberries, and strawberries. Those are the fruits most likely to contain harmful pesticide residues. The rule only applies to fresh fruit. Canned peaches, for example, are among the least contaminated fruits. (So are fresh bananas, blueberries, kiwis, mangoes watermelon, and canned pineapples).
(Source: Nutrition Action Health Letter, June 2003, Volume 30/Number 5.)