A standing-water audit is a ten-minute walk around your home where you hunt down every container, crack, and low spot holding water — because that water is where mosquitoes breed, and killing it kills the next generation before it can fly. Female mosquitoes need only a bottle cap's worth of standing water to lay eggs, and those eggs become biting adults in about 7–10 days. So the audit is the single highest-value chore in mosquito control: do it once a week and larvae never graduate to adulthood. Here's the full checklist, in the order you'll walk it.
This is the hands-on companion to our free source-reduction playbook — that post is the why; this one is the do it right now.
Why does a standing-water audit work so well?
Because mosquitoes are 100% dependent on standing water for the first half of their lives. Eggs, larvae ("wigglers"), and pupae all live in water — they can't fly, hide, or escape. Both the CDC and EPA rank source reduction (getting rid of that water) at the very top of the mosquito-control hierarchy, above sprays and repellents, for exactly this reason. You're not fighting the adults buzzing your ears; you're deleting them before they hatch. It's the difference between mopping the floor and turning off the faucet.
The 10-minute standing-water audit checklist
Grab your phone (for the timer and to snap photos of repeat offenders) and walk your whole property in one loop. For each item: dump it, flip it, drill it, or dose it. (Dump the water, flip the container so it can't refill, drill drainage holes if it's a bin, or dose it with Bti if it's water you can't remove.)
Zone 1: The backyard and patio
- Plant pots and their saucers. The #1 backyard breeding site in the city. Every saucer under every pot holds water after rain or watering. Dump them — or ditch the saucers entirely.
- Buckets, watering cans, wheelbarrows. Store them upside down. An open bucket is a mosquito nursery within a week of rain.
- Tarps and covers. Grill covers, furniture covers, and pool covers sag into water-holding pockets. Tighten them or pitch them so water runs off.
- Birdbaths and fountains. Refresh weekly, or add a small pump — mosquitoes need still water, so movement helps.
- Kids' toys, sandbox lids, dog bowls, saucer sleds left out in the yard.
- The kiddie pool / inflatable pool. Empty and flip when not in use.
Zone 2: The building's edges
- Clogged gutters and downspouts. A leaf-packed gutter is a hidden trough of stagnant water running the length of your building. Clear them at least twice a season.
- The AC condensate tray / drip line. Window units and drainage trays collect water right outside your window.
- Corrugated (ribbed) drainage pipe. Those black extension pipes hold water in every ridge. Straighten them so they drain, or swap for smooth pipe.
- Basement areaway and window wells. The sunken space in front of a brownstone's basement door collects rainwater and leaves.
Zone 3: The stuff New Yorkers always miss
- Trash and recycling bin lids and rims. City bins pool water beautifully. Drill a couple of drainage holes in the bottom of any bin that catches rain.
- Clogged catch basins and yard drains. If water isn't draining, it's breeding.
- The alley, side passage, or shared airway between buildings, where junk and puddles collect out of sight.
- The vacant lot or neglected yard next door. Not yours to clean, but very much your problem — worth a 311 call (see below).
- Anything with a rim that traps a puddle: old tires, boat covers, construction debris, upturned frisbees.
What do I do with water I can't get rid of?
Some water can't be dumped — a rain barrel you use for the garden, a small pond, a low spot that always floods, a birdbath you love. You don't need it gone; you need it lethal to larvae. That's the job of Bti (Bacillus thuringiensis israelensis), a naturally occurring soil bacterium that kills mosquito larvae and is safe for pets, birds, fish, bees, and people. It comes in two formats:
We break down exactly how Bti works and why it's safe in Bti Explained. The short version: dunks for the big stuff and slow release, bits for fast knockdown and small containers.
How often should I do the audit?
Weekly, from May through September, and again within a day or two of any heavy rain — a big storm refills every container and low spot you just emptied, essentially handing you a new crop of breeding sites. The first, most thorough audit of the year should happen in April, before mosquito season really starts, so you cut off the early broods that would otherwise multiply into the late-summer swarm. See the full month-by-month plan in our NYC mosquito season timeline.
What about my neighbor's yard and the vacant lot?
Here's the frustrating truth of NYC blocks: the tiger mosquito biting you barely travels 150 feet, so one messy yard on the block can undo everyone's careful audits. Two moves:
- Talk to neighbors. Coordinating even a few adjacent yards is the single highest-leverage thing you can do — the entire premise of the Bed-Stuy Mosquito Pilot.
- Report standing water you can't fix. In NYC, call 311 or file online to report standing water, abandoned pools, and mosquito conditions on properties that aren't yours. The city follows up.
The bottom line
- A standing-water audit is a 10-minute weekly walk that finds and kills mosquito breeding sites — the top-ranked control per CDC and EPA.
- For each source: dump it, flip it, drill it, or dose it with Bti.
- Hit the backyard, the building edges, and the sneaky spots New Yorkers miss (bin lids, catch basins, AC trays, corrugated pipe).
- Treat un-dumpable water with Bti (dunks for big/slow, bits for small/fast).
- Re-audit after every big rain, and coordinate your block for what you can't reach.
Ten minutes a week beats every gadget in the store. Start the clock.
Player questions
How do I find mosquito breeding sites around my home?
Walk your whole property in one loop and check every spot that can hold water: plant saucers, buckets, tarps, birdbaths, clogged gutters, AC drip trays, corrugated drainpipe, trash-bin lids, catch basins, and low spots. A female mosquito needs only a bottle cap of standing water to breed, so inspect small containers, not just obvious puddles.
How long does water have to sit before mosquitoes breed in it?
Females can lay eggs in standing water almost immediately, and the eggs typically develop into flying adults in about 7 to 10 days, faster in hot weather. That's why emptying every water source once a week works: nothing survives long enough to reach the biting adult stage.
What is the most common mosquito breeding site in a backyard?
Plant pots and the saucers under them are the number-one backyard breeding site in NYC — nearly every saucer holds water after rain or watering. Clogged gutters, forgotten buckets, tarps that sag into pockets, and birdbaths are close behind. All of these are things you control, which is why source reduction is so effective.
What can I put in standing water I can't remove?
Use Bti (Bacillus thuringiensis israelensis), sold as Mosquito Dunks and Mosquito Bits. It's a naturally occurring bacterium that kills mosquito larvae but is safe for people, pets, fish, birds, and bees. Dunks slowly release for about 30 days in larger water like rain barrels and ponds; granular bits give a faster knockdown in small containers.
How often should I check for standing water?
Weekly from roughly May through September, plus an extra check within a day or two after any heavy rain, since storms refill everything you just emptied. Do your most thorough audit in April, before mosquito season ramps up, to eliminate early broods before they multiply into the late-summer swarm.
What if my neighbor's yard has standing water?
Because NYC's tiger mosquitoes rarely travel more than about 150 feet, a neighbor's breeding sites become your problem. Talk to them first if you can — coordinating adjacent yards is the most effective move. For abandoned properties or unresponsive owners, call 311 or file online to report standing water; the city follows up on complaints.