Why they are both Beneficial & Pest
Butterflies themselves are not a pest as they don’t eat plants feeding instead on nectar and pollen. In fact they are important pollinators of plants.
It is their larvae, the caterpillars, that can cause so much destruction.
As with many insects in the garden, it is important to observe just how much damage is being done and if it is really a concern.
Ideally, we should discourage them from laying the eggs on our vegetables in the first place,
The caterpillars of all butterflies need to eat something, but many of them don’t harm our vegetables and the adults are extremely beautiful. For example the larvae of the Orchard swallowtail butterfly (Papilio aegeus) occasionally does a small amount of damage to citrus trees, but not enough to really be a pest.
Some are pests of specific plants, such as the Cycad blue butterfly (Theclinesthes onycha) and Cabbage white butterfly (Pieris rapae). The cycad butterfly has never bothered us, but if you are attached to your cycads then you would want to watch out for it. We’re always on the lookout for the cabbage white butterfly, as it can do extensive damage to vegetable crops.