Mosquitoes and rain totes

Where mosquitoes get in

A mosquito needs a small opening and still water. A tote of rainwater provides both. The openings are the top fill, the overflow pipe, the vent and any gap around the lid. Each one needs a screen, and the screen has to be fine enough to stop a mosquito, which means fine mesh, not a garden-hose strainer.

Check the screens after every storm. A leaf mat can tear a screen off a gutter inlet, and a lid that has shifted leaves a gap that nobody sees.

Other ways to keep the water clean

• Keep the tote covered so no light reaches the water.
• Use the water; stagnant water is worse than moving water.
• Empty and wash the tote if you find larvae or a green film.
• Never add chemicals to the tote to kill larvae without checking they suit your plants.

Why it matters here

Riverside and San Bernardino counties have mosquito and vector control districts that run public programmes. A rain tote left open is the kind of standing water they ask residents to remove. Ask your district about local rules and about mosquitofish programmes.

See catching rain in a tote for the whole system and lids and caps for the closures.

Checking a screen after a storm

After heavy rain, walk to the tote with a torch. Look at the inlet screen for leaves, grit or a torn corner. Look at the overflow pipe to see that water has gone where you intended. Lift the lid edge and check that the seal is seated, because a lid knocked sideways by wind is an open door.

Tip the tote slightly if you can and look for movement in the water: wrigglers hang at the surface and dive when disturbed. If you find any, drain the tote, rinse the surface, repair the screen and refill. A five minute check each month is cheaper than a mosquito season.

Screens for different openings

A flat mesh disc works on a round fill. A sock of mesh over an overflow pipe works well. A mesh vent cap fits the breather. Use stainless or plastic mesh; aluminium corrodes in some rainwater.

Questions people ask