Beneficial Nematodes and Castile Soap: Compatibility for Flea Control

Direct Answer

Castile soap does not control fleas and will not harm beneficial nematodes, but it's ineffective for the stated purpose.

Effective Organic Flea Control

• On pets: Dust with rotenone (botanical insecticide). Kills fleas, lasts ~1 day in sun, low human toxicity. Apply at night, wash off morning. Restrict garden use to avoid harming beneficial insects.
• In yard: Beneficial nematodes (Steinernema carpocapsae) applied to moist soil control flea larvae. Water before and after application.
• Indoors: Vacuum daily; wash pet bedding in hot water; use diatomaceous earth in cracks.

Safety Note

Rotenone is toxic to fish and bees. Avoid runoff to waterways. Do not use on edible crops near harvest.