Here is the Dirty Dozen, the top 12 fruits and veggies that I most highly recommend that you purchase organic because conventional produce is sprayed more heavily with pesticides:
Sweet Bell Peppers
Also: Green beans and kale are moving up on the most sprayed list as well.
Here are the Clean 15. These are the fruits and veggies that you can eat conventionally because they are not sprayed as heavily with pesticides.
Sweet Corn (watch for GMO)