The tried and true approach is BT (bacillus thurigensis). It is a naturally occuring bacteria that is toxic to caterpillars only. It is available as a dust or a liquid, ready to use or in concentrate. The other safe, organic control besides hungry birds and hand-picking is Spinosad, available under different product names. Sevin and other things can work too, but they are nor organic and too wide spectrum- also can be harmful to bees.
Some plants are host for butterflies like milkweed, butterfly bush, hollyhock,and passion fruit vines. BT is usually for tomato and tobacco hornworms, budworms, corn earworms, and cabbage moths that destroy our edible crops. Note: caterpillars are larva of moths and butterflies. Fly and beetle larvae, including fruit tree borers are not. They require different products.