Larvae, not adults
Best mosquito dunks
The best mosquito dunk is a Bti product in water you cannot dump: a rain barrel, a ditch the county will not drain, an unused pond edge the label allows. Mosquito larvae are the target. Adults already biting you are not. Dump the pot saucer, clean the gutter, and screen the window before you buy a second dunk. A backyard fogger does not replace that.
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Best for a barrel or a pond edge: Mosquito Dunks (Bti larvicide). A dunk treats a labeled volume for weeks. Break a piece only if the label tells you how. Do not toss dunks into a birdbath you could have dumped and scrubbed.
Compare the picks
| Role | Tool | Best for | Type |
|---|---|---|---|
| Best for a barrel or a pond edge | Mosquito Dunks (Bti larvicide) | Water that has to stay | Labeled product |
| Best granules | Mosquito Bits (Bti granules) | Saucers, catch basins, and fungus-gnat soil | Labeled product |
| Best adult barrier | Window screen repair kit | The torn window you are dunking around | Hardware |
Which one to buy
Labeled product
Mosquito Dunks (Bti larvicide)
Best for a barrel or a pond edge — A dunk treats a labeled volume for weeks. Break a piece only if the label tells you how. Do not toss dunks into a birdbath you could have dumped and scrubbed.
Labeled product
Mosquito Bits (Bti granules)
Best granules — Bits spread into smaller volumes and into potting soil when the label allows. Same active idea: Bti, larvae only. Empty what you can empty first.
Hardware
Window screen repair kit
Best adult barrier — A dunk in the yard does not close a ripped screen. Patch the screen if the bites happen indoors at night.
Dump before you dunk
The breeding sites that matter in a yard are small: saucers, tires, a tarp crease, a clogged gutter, a kid’s bucket. Those get dumped and scrubbed. Bti is for water that has a reason to remain. Treating a birdbath with Bti and never changing the water is worse for the birds than a weekly scrub. Read the label for animal water and ornamental ponds. Some sites are allowed and some are not.
Common questions
Do mosquito dunks kill adult mosquitoes?
No. Bti kills larvae in the water. Adults already on the wing need a screen, a repellent on skin, and fewer breeding sites.
Dunks or bits?
Dunks for a larger labeled volume that sits for weeks. Bits for smaller spots and for soil fungus gnats when that use is on the label.
Are dunks safe for fish and pets?
Bti is selective compared with many adulticides, and the label still lists where it may go. Do not assume a fish pond, a dog bowl, or a vegetable garden is an allowed site. Read the panel.