Mosquito Dunks are small, beige, donut shaped tablets that float on standing water and slowly release Bti, a naturally occurring bacterium that kills mosquito larvae. The larvae take in the Bti as they feed, which stops them before they mature into biting adults, and each dunk keeps working for 30 days or more.

What is Bti, and how does it kill larvae?

Bti, short for Bacillus thuringiensis israelensis, is a bacterium whose toxins break down the gut lining of mosquito larvae after they eat it. It is also lethal to the larvae of fungus gnats and blackflies, while its direct effects on other organisms are considered negligible.

Why does a mosquito dunk float?

So it stays at the surface and releases its Bti a little at a time. As the dunk floats, it slowly dissolves and keeps the water treated for 30 days or more, rather than releasing everything at once.

How is a mosquito dunk used in small containers and large ponds?

By matching the dose to the water's surface area. For a birdbath, bucket, or other container smaller than 100 square feet, a piece broken off one of the Mosquito Dunks treats the water, while a larger pond takes one whole dunk for every 100 square feet of surface.

Frequently Asked Questions

What happens when a dunk fully dissolves?

It is replaced. A fresh dunk is added every 30 days or once the old one has dissolved, whichever comes first.

Does water depth change how a dunk works?

No. Each dunk floats and treats up to 100 square feet of surface water, regardless of depth.

Can mosquito dunks be used in planters?

Yes. Planter reservoirs that hold standing water are among their listed uses.

Why do some mosquitoes still turn up after treatment?

Hidden breeding spots. Some species, including Aedes aegypti and Aedes albopictus, breed in small, hidden containers that are easy to miss. Every container that holds water needs to be found and treated.