Mosquito Control in Rain Barrels: Safe Bti Treatment for Garden Use

Even with a screen, mosquitoes lay eggs in rain barrels. The safe, effective solution is Bti (Bacillus thuringiensis israelensis)—a bacterial larvicide specific to mosquitoes, blackflies, and fungus gnats.

How to Use

• Buy Bti "dunks," "bits," or granules (brands: Mosquito Dunks, Mosquito Bits, Summit).
• Follow label: typically 1 dunk per 100 sq ft of water surface, effective 30 days.
• Safe for plants, pets, wildlife, birds, fish, and humans. Used in cattle troughs, bird baths, irrigation ponds.
• Does not affect water quality for garden irrigation.

Additional Tips

• Keep the screen tight; repair tears.
• Use a floating cover or oil layer (minimal) as a physical barrier.
• Empty barrels weekly if not using Bti (breaks the 7–10 day larval cycle).

Do not use bleach, oil, or chemicals—they harm plants and soil life. Bti is the standard for potable and irrigation water containers.