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DEEP FILE · THE YARD WALKTHROUGH

One lap, twelve mosquito breeding sites.

This is the survey as we would run it: one flashlight, one bucket, ten minutes, in the order containers actually turn up positive. Each stop logs what you see, why it breeds, the move, and the clock you are racing. Bring gloves; leave with a drier yard.

01Before the lap

Three items, no shopping required: a flashlight (larvae sit at the surface, invisible from above without side light), a bucket or trug (every container you empty needs somewhere to go), and gloves. Pick the hour: morning after rain is ideal, because everything that caught water overnight is full and visible.

02The twelve stops

STOP 01Plant pot saucers

The classic. Aedes eggs glue to the inner wall just above the waterline and survive months dry; the first refill hatches them. Look at the water surface with side light: larvae hang like tiny commas, tail up. The move: tip the water on the soil, scrub the saucer wall with your thumb, done. Weekly in season. Why first: highest positivity of any container class in CDC surveillance rounds.

Plant saucer full of water with larvae at surface, thumb scrubbing inner wall PLATE 101
The highest-positive container in surveillance rounds. The fix is a thumb, not a chemical.
  • Larvae hang at the surface: commas, tail up
  • Scrub the wall above the old waterline: eggs are glued there
  • Pour the water into the soil, not the drain

STOP 02Open buckets and watering cans

One neglected bucket can seed a street block: Aedes stay within roughly a hundred meters of where they hatch. The move: tip and store upside down, or lid tight. A watering can with its rose attached holds a perfect dark reservoir; unscrew it and shake it out.

Two buckets: one holding dark rainwater, one overturned dry on gravel PLATE 102
The whole fix in one frame. Left bucket seeds a street; right bucket is storage done right.
  • Water + leaves: organic, shaded, Aedes-ready
  • Upside down: no water, no eggs, done

STOP 03Roof gutters

You cannot see into them from the ground; that is the point. Culex territory: organic-rich water, shade, a night biter's nursery. The move: run water from a hose at the downspout end and watch it exit; if it does not exit, clear from the far end with a plumber's snake or a blower. The tell that you missed one: mosquitoes at dusk that were not there at noon.

Roof gutter with pooled water dammed by leaves, trowel approaching PLATE 103
Invisible from the ground, which is the point. Flush the downspout end; if water will not exit, clear from the far end.
  • Leaf dam: water pools behind it
  • Dark surface film: days old, larvae likely
  • Gloved trowel: clear the dam, flush again

STOP 04Folded tarps, pool covers, swing canopies

Every fold is an independent puddle, and a tarp over a boat or firewood holds ten of them. The move: pull it taut, or re-fold so the folds point down. Shake out weekly in season; a thirty-second shake replaces a week of breeding.

Folded tarp over firewood with puddles in each fold, hand re-folding PLATE 104
Every fold is an independent puddle. Re-fold so the creases point down, or pull it taut.
  • Sky-reflecting puddle: fold holds water
  • Slack fabric: pools form wherever it dips
  • Hand re-folds taut: thirty seconds replaces a week of breeding

STOP 05Birdbaths

The one container people deliberately fill. The rhythm is the fix: a full dump-and-scrub every five days beats any chemical, because the seven-to-ten day egg-to-adult window cannot complete. The move: empty, quick scrub to dislodge eggs at the waterline, refill.

Stone birdbath with green water, brush scrubbing the waterline ring PLATE 105
The one container people fill on purpose. A full dump-and-scrub every five days beats any chemical.
  • Green tinge: algae plus days of standing
  • Scrub the ring at the waterline: eggs sit above it

STOP 06Children's toys

Sandboxes with a lid that catches rain, dump trucks left hub-down, slides with molded footwells. All pool. The move: a quarter-inch drain hole in the lowest point of anything that lives outside, or bring them in. The hole does not ruin the toy; the water ruins the evening.

Toy dump truck holding rainwater, drill making drain hole in lowest corner PLATE 106
One quarter-inch hole in the lowest point of anything that lives outside. The hole does not ruin the toy.
  • Hub-down truck: a perfect dark reservoir
  • Drain hole at the true low point: water leaves on its own

STOP 07Trash and recycling bins

Both the bin and its lid hold water: the lid's rim faces up and catches rain invisibly. The move: drill two drain holes in the lid rim, store bins tilted, and keep the bin itself lidded tight.

Trash bin lid rim facing up holding rainwater, drill at work PLATE 107
The lid's rim faces up and catches rain invisibly. Two drain holes close the case.
  • Lid channel: an inch of rain sits here
  • Drill two holes in the rim, store bins tilted

STOP 08Pet water bowls

Warm, organic, refreshed daily: the perfect nursery, but only if the rhythm breaks. The move is the cheapest on this page: dump and rinse daily when you refresh. Doing it during the same trip as feeding builds the habit.

Steel pet bowl being emptied into kitchen sink, water mid-pour PLATE 108
The cheapest move on the page. Empty and rinse during the same trip as feeding.
  • Same trip as feeding: the habit is the fix

STOP 09Rain barrels and cisterns

The containers you cannot tip. This is the one stop with a product answer: a fine mesh lid (mosquitero) on every opening, and Bti inside, per label. A barrel without a lid is a mosquito farm with a tap. See the Bti section below.

Rain barrel with mesh screen lid being pressed over rim, downspout above PLATE 109
The container you cannot tip. Fine mesh on every opening, Bti inside per label.
  • Mesh fine enough to stop a mosquito: not cheesecloth
  • Elastic edge pressed tight: no gaps
  • Downspout must enter through the mesh, not beside it

STOP 10AC drip pans and condensate lines

A unit running in summer produces a steady trickle: constant water, constant shade. The move: check that the line drains to soil or a drain, not a low spot; if the pan itself stands, give it a weekly glance and a wipe.

AC unit with condensate line ending in damp patch, shallow pan half-full PLATE 110
Constant trickle plus constant shade. The line must drain to soil or a drain, not a low spot.
  • Damp patch: the line ends in a puddle-in-progress
  • Pan half-full: one weekly glance and a wipe

STOP 11Tree holes and stumps

Natural containers, easy to forget because they look like landscape. A rot-pocket in a trunk holds liters invisibly. The move: fill with sand or expandable foam; do not leave an open cup of organic water at knee height.

Tree rot pocket holding dark water, hand filling it with sand PLATE 111
Natural containers that look like landscape. Fill with sand or foam; do not leave an open cup at knee height.
  • Rot pocket: liters hide invisibly inside the trunk
  • Sand fill: permanent, cheaper than any gadget

STOP 12The property line

The last stop is the walk itself: fence-line planters, the neighbor's tire you can see over the fence, the shared drain. You cannot fix the neighbor's yard; you can fix what drains onto yours. And Aedes being hundred-meter mosquitoes, your lap matters more than their pond.

Fence line: own side tidy with overturned pots, neighbor side with a water-holding tire PLATE 112
You cannot fix the neighbor's yard. Fix what drains onto yours; being hundred-meter mosquitoes, your lap matters more.
  • Your side: overturned, drained, done
  • Their tire: report to the municipality, do not trespass

03The clock you are racing

Egg to biting adult takes seven to ten days in warm water. Every stop above is the same race against the same clock: interrupt the water within the window and the eggs die with it. Miss it and the yard resets to zero mosquitoes in about a week. That is why the survey is weekly in season and monthly out of it, not once: the clock restarts with every rain.

04Is Bti larvicide harmful to people and pets?

Is larvicide harmful to humans? Bti at label rates is not: Bacillus thuringiensis israelensis is toxic to mosquito and blackfly larvae, harmless to pets, birds and people when used as labelled, and registered for residential use by the US EPA. Use it on water you keep (rain barrels, ornamental ponds, cisterns). Granules or briquettes, per the label: a briquette lasts about thirty days; granules go in on a monthly rhythm. It does not repel adults and does nothing for pupae: match it to the calendar, not to the panic.

Container-positive ranking: CDC container surveillance guidance and WHO dengue vector surveys. Development window: WHO dengue guidelines (2009) ch. 2. Bti: US EPA registered larvicide labeling. All checked 2026-09.

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