Any of the caterpillars of moths and/or butterflies can be controlled with Bt (Bacillus thuringiensis) and not hurt the beneficials. To avoid hurting butterflies, carefully treat just the infested plants. An even safer approach is to release trichogramma wasps which are inexpensive and very effective. Do not use Sevin. Although having a reputation being a low toxicity product, it is one of the most toxic products still on the market. Just as it says on the label, it is severely deadly to bees and other pollinators.