Chemical-Free Mosquito Control

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[5] Empty all miscellaneous standing-water sources. Any receptacles that hold water-old bottles, tin cans, water troughs, barrels, children's wading pools, and undrained boatsshould be emptied, removed, covered, or turned upside down. Change the water in pet dishes daily and birdbaths twice weekly, washing them as you do so. Either discard old tires or store them indoors. Screen any rain barrels and openings to water tanks, cisterns, and wells. Repair leaky plumbing and outside faucets, and check drain outlets from air conditioners. Clean leaf-clogged roof gutters and drain flat roofs. Finally, fill holes in trees with sand or mortar, or drain them when necessary.

BIOLOGICAL CONTROL

Biological control doesn't work as rapidly as chemicals, but it can be longer-lasting and environmentally safer. For this reason, some peo ple encourage mosquito-eating toads to take up residence in their yards, while others build special birdhouses for such insect-gobblers as purple martins. On the southern coast of Maine, dragonflies—which dine on mosquito larvae and adults both—are utilized instead of poisonous sprays. There are, however, other mosquito predators and parasites that may not be as familiar.

For ponds large and deep enough to support fish, several mosquito-controlling species are available:

The mosquito fish (Gambusia affinis) is considered to have the best potential. It's only about two-and-a-half inches long, but it's been credited with reducing mosquito propagation in ponds by 80% to 95%. Use ten to twelve fish for a pool with a surface area of about ten square yards. They reproduce quickly, but automatically slow their birth rate when their density threatens to outrun the supply of mosquito larvae and other food. They like shallow areas with little current and will tolerate a fair amount of pollution. They don't, however, survive northern winters, so a yearly stocking program would have to be implemented in cold-weather areas.

Fathead minnows (Pimephales promelas) are primarily bottom and midwater feeders and are good for mud-bottomed, shallow waters such as flooded fields, ponds, and ditches. They need water temperatures of 64°F to spawn and can produce several broods per season.

Golden shiners (Notemigonus crysoleucas) like clear, well-vegetated ponds, though they will tolerate some pollution and can live in warmwater swamps. They need 60° to 80°F water to produce young, which feed primarily on algae and microcrustaceans. These fish are especially good for small farm ponds.

Goldfish (Carassius auratus) prefer clear, quiet pools with submerged vegetation, though they, too, can survive a moderate amount of pollution and a high content of organic matter. They don't spawn until they are about two years old but are prolific after that. Naturally, they are perfect for ornamental ponds, though they are not effective on certain mosquitoes of the permanent pool group.

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