The idea that dishwashing liquid is a mosquito repellant is a myth, and it's inaccurate. That doesn't mean that dishwashing liquid isn't useful for mosquito control. Because of its ability to reduce surface tension, a thin film on water can drown both larvae and adult mosquitos. There's nothing in dish liquid -- not even lemon-scented products -- that repels mosquitoes, though.
About that Lemon Scent
One of the most-quoted recipes for dish-detergent mosquito repellant spray calls for lemon-scented detergent, and the reason may be the notion that lemons repel mosquitos. Lemon oil may or may not be an effective repellant, and although citrus-based sprays are often recommended for mosquito control, the idea may exist because many herbs and oils with lemony-sounding names repel mosquitoes.
- Oil of Lemon Eucalyptus -- One of the most effective natural insect repellents, according
</ahref="http:>to the Centers for Disease Control, oil of lemon eucalyptus has nothing to do with lemons. It comes from Eucalyptus citriodora, a species of eucalyptus tree. The active ingredient is cineole.
- Citronella Oil -- Although it sounds like it might be related to citric acid, which is abundant in lemons, citronella is derived from grasses. According to the National Pesticide Information Center, citronella repels insects by masking scents, thus discouraging them from homing in on your succulent flesh.
- Lemongrass -- The oil derived from lemongrass (Cymbopogon) is a natural mosquito repellant. The plant itself also deters mosquito. Lemongrass prefers warm, moist climates and can be grown outside in U.S. Department of Agriculture zones 9 to 11.
- Lemon Balm -- An herb with a high concentration of citronellal -- which, like citronella, is a mosquito repellant -- lemon balm (Melissa officinalis) can be crushed and rubbed on the skin to repel mosquitos.
Dish Detergent for Mosquito Control
Standing water anywhere on your property is a mosquito magnet, but when you can't simply dump it out, add dishwashing detergent to it; a teaspoon treats a 50-gallon barrel. Because it reduces surface tension at the surface of the water, any mosquito that lands there will sink instead of walking blithely on the surface, laying eggs and flying away. Moreover, any larvae already in the water will be unable to breathe and will drown.