Apply BT (Bacillus thuringiensis) to stored combs

Spray or dust stored combs with Bacillus thuringiensis var. aizawai (Bt-a) before stacking them for storage. Bt-a produces a crystal protein toxin that is specifically lethal to wax moth larvae when ingested, while remaining harmless to bees, humans, and other non-target insects.

Why It Works

Bt-a toxin binds to receptors in the alkaline gut of Lepidoptera larvae (moths and butterflies), causing the gut wall to rupture. Wax moth larvae that feed on treated comb die within 2-4 days. The toxin has no effect on Hymenoptera (bees), making it safe for combs that will be returned to hives. Bt-a is approved for use in certified organic beekeeping by the USDA National Organic Program.

Tips

• Apply Bt-a as a light mist on both sides of each frame before storage — the product sold as Certan (B401) is formulated specifically for beekeeping use
• Bt-a is preventative, not curative — apply to clean combs before moth larvae establish; it will not control an active heavy infestation
• Reapply annually, as Bt-a degrades over time with UV exposure and humidity
• Store treated combs in a cool, dry location to maximize Bt-a longevity