I have always been concerned about what is on the fruits and vegtables I buy in the store because I really don’t know where they have been and what type of sprays could have been used on them. EWG (Environmental Working Group) came out with handy grocery list for what produce you should definitely try to buy organic and what you can get away with not buying organic (and save yourself some pennies) based upon the pesticide level detected. Here is a visual:
However, whether you buy organic or not, ALWAYS wash your fruits and veggies well! 
Here is a Produce Washing Tonic recipe I found at Passionate Homemaking.
Produce Washing Tonic
Adding a bit of lemon juice or 3-4 drops of grapefruit seed extract can give it an extra boost!
3 cups filtered water
3 Tbsp white distilled vinegar or apple cider vinegar
2 Tbsp baking soda
Mix ingredients together in a spray bottle. Spray it on fruits and vegetables. Rinse well with cold water. You may also combine in the sink to dunk your produce if you desire to wash in large batches. This tonic is not recommended on mushrooms as they will absorb the flavor.
Produce Washing Tips
1. Use a scrub brush for root vegetables, and produce with rinds, groves or waxy surfaces, and rinse well. This includes melons!
2. Discard outer leaves of leafy vegetables. Rinse each leaf individually. Make sure they are dry before storing in the refrigerator as moisture can encourage the growth of bacteria.
3. Wash more tender fruit (berries, grapes, etc) in a colander.
4. Cut produce on a clean cutting board with a clean knife.
5. Thaw meats on a separate tray or plate in the refrigerator to prevent meat juices from dripping into produce drawers.
6. Clean and sanitize the refrigerator produce drawer regularly.
