I watched this wonderful film a few weeks ago called "Back to Eden" about a man who gardens the way nature intended. He doesn't water! You can watch it online. It is really lovely.
He makes his own pesticide of Hot peppers and garlic and blends them up and sprays the trees if needed.
But his general attitude is
1. If his plants/trees are strong enough then the pests won't kill them.
2. His plants are so moist that the bugs can't handle the moisture and move on.
3. If he does have leaves with bug bites, then that means the plant is healthy and nutritious.
He had a whole flock of crows that were just decimating his apple trees at one point. He shot one and then hung it on a stake by the trees and when the crows came back the next morning they promptly turned around and never ate the apples again.