Last week I began a discussion on West Nile virus and your yard.
If you read it, skip to the next paragraph. If you missed it, it is important to remember that most people infected with the West Nile virus will not experience any illness. About 20 percent will develop West Nile fever, and less than ½ of 1 percent will develop a more severe form of the disease.
To reduce your chances of exposure to WNV, reduce the local mosquito population. Seek out and drain sources of stagnant standing water where young mosquitoes can feed and grow. Active, well-maintained water features are not breeding sites for mosquitoes. Chlorinated swimming pools and clean, bubbling fountains with chlorine or other mosquito blocking additives are not a problem. Fish ponds are not a problem. Fish eat mosquitoes, as eggs, larvae, pupae or adults. Enjoy them if you have them, and do not hesitate to add a water feature to your yard.
Once you start looking, you may be surprised where stagnant water can collect. Check everywhere. A baggy grill cover can have a hidden pool. Check that a flat roof drains completely. Check rain gutters for clogs and clean them out. Check for trash, such as bottles or other containers, in places that may be hard to see, like under dense bushes. If you have older trees with hollows in them, cover the opening with a piece of window screen to keep out mosquitoes. Horticulturists no longer advocate drilling out or filling in such cavities.
One prime mosquito breeding site is old tires. Remove them from your property. If a neighbor has a pile of tires, you can legally ask them to remove them. If they refuse, the Pima County Health Department will issue warnings and then costly citations until such health risks are eliminated.
If you use an evaporative cooler, drain it completely at least once per week. You can attach a hose to the drain outlet and use the relatively fresh water on your plants. Better yet, drain it once daily, and double the life of your cooler pads. If you have a cooler but switched to air conditioning for the monsoon season, drain and dry the cooler completely. Cover it to keep monsoon rain from getting in.
Keep mosquitoes out of your home. Install or repair window and door screens. Most evaporative cooler pads are dense enough to keep mosquitoes out, but you can consider adding a screen across the space where the air enters your home. Note that this will decrease the operating efficiency.
Protect yourself from mosquito bites. Consider staying indoors at dawn, dusk, and in the early evening, which are peak biting times for the Culex mosquito. Apply insect repellent to exposed skin and thin clothing when going outside for extended periods. While the CDC recommends DEET based repellents, repellents made from lemon-scented herbs are also useful.
Repellents may irritate the eyes and mouth, so avoid applying repellent to the hands of small children. Whenever you use an insecticide or insect repellent, be sure to read and follow the manufacturer's directions. Place mosquito netting over infant carriers when you are outdoors in evening.
It is not advisable to spray your yard against mosquitoes. Mosquitoes can fly upwind well over a mile to a food source (as detected by carbon dioxide exhaled). Spraying will merely create a vacuum for more insects to move into. In our reading area there are over 10 species of bat, as well as night-flying birds, that consume mosquitoes and other insect pests. You could build a bat house to invite mosquito eaters to your yard, but that is a topic for another day.
Jacqueline has been gardening in the Southwest since childhood. Dr. Soule has been writing articles about how to garden successfully in our area for over two decades. Look for her column in these pages every week.