From New Scientist:
All fruit and vegetables contain large numbers of naturally occurring pesticides. These are the result of an arms race with insect herbivores.
If we tested for these, we would find that they are just as nasty as synthetic pesticides, but present in food in higher amounts. However, they don't affect us when we consume them because their concentration is only effective against insects, not anything large.
The real problem with organic farming is low yield. You need much more land to obtain similar yields to other forms of farming. I think we should be returning farmland to nature, not increasing its area.