Hey Mate,
Quite hard to define, especially outdoors where every kind of pest moves around. I would go with companion plants on the next run. There are a couple of, like Calendula which scares away some sorts of caterpillars, coriander amells disgusting to some flies, lemon balm is also a natural repellent because of its odor.
My Diesel Auto is outside in a bed full with companions. (Have a peek)
Some for food, some for protection.
Good luck and happy trails for the rest of the way.
Cheerz
OimRausch