Lye vs. Lime on Flowers: Safe Organic Pest Control for Caterpillars

A reader asked about using lye on flowers for caterpillars—absolutely not. Lye (sodium hydroxide) kills everything: plants, bees, soil life. The follow-up clarified lime (calcium carbonate). Lime is a soil amendment to raise pH in acidic soils, not a pesticide.

For caterpillars, use Bacillus thuringiensis (Bt)—a bacterial spray toxic only to caterpillars when ingested. Apply at first sign of feeding. Hand-picking and relocating works for small infestations. As a last resort, pyrethrin/rotenone blends (evening only to spare bees) can be used, but they harm beneficials too.

Best long-term strategy: build healthy soil with compost, mulch, and diverse plantings. Vigorous plants resist pests; weak ones attract them.