Picture this: a balmy evening, the perfect time to dine outside, and company is about to arrive. You’ve just invested in a new high-tech outdoor kitchen. While sipping a cool drink, a familiar whine suddenly changes everything. Diving close to your ears, pausing long enough for a quick bite, one mosquito can wreck all your plans. Dinner is quickly moved into the house, hopefully without letting in the unwanted guest.

We can reduce the numbers of this annoying creature if we all follow a few common-sense suggestions.

The mosquitoes that bite us are adult females of several species. Some bite at dawn, others at dusk. The adult males feed on flower nectar instead.

The female needs our blood or the blood of other animals to develop eggs, and she needs standing water in which to lay the eggs. The larvae grow, feeding on microorganisms and organic matter in the water. In a few days, mosquitoes emerge. An uncovered hot tub with standing water may produce thousands of mosquitoes in just a few days.

The female can spread disease, including West Nile virus. Birds are hosts to this disease, so when a mosquito bites an infected bird, it can then transfer the disease to us. Only a few cases have been reported in the United States, mainly in elderly people, according to the Centers for Disease Control and Prevention. However, you should never pick up a dead bird with your bare hands.

Killing larvae by getting rid of standing water is much more effective than spraying with pesticides. Pesticides kill only a few adult mosquitoes at best, while also killing beneficial insects and bugs. Never use pesticides on storm drains, catch basins or storm gutters as this water goes directly to the bay. It is better to unclog storm drains to promote flowing water.     

Take a walk around your garden. Turn plant saucers upside down, and refresh dog water dishes every day. Change the water in birdbaths every day or at least weekly.

The Napa County Mosquito Abatement District has useful brochures with checklists to help you find standing water. A tree hole partially filled with water in species such as eucalyptus, oak, bay laurel, sycamore and elm is the perfect breeding ground for the Western Tree-hole Mosquito, which is responsible for canine heartworm in Napa Valley. Fill holes with sand, cement or polymer granules after consulting with a tree expert.

Another trouble spot is old tires. Their form makes emptying water difficult.

In creeks, watering troughs, septic tanks and ponds, mosquito fish can keep mosquitoes under control. The fish breed every few weeks, grow to about two inches and don’t need to be fed, but they do need protection from pesticides and predators like raccoons. They are available free from the Mosquito Abatement District. Call (707) 553-0610 for more information.

For personal protection, you can swath your guests in mosquito netting, or use insect repellents. When mosquitoes are active, wear protective clothing. They have a way of finding unprotected skin. Lights near entrances may attract mosquitoes.

DEET-based repellents have been found to work efficiently and safely by Our Water-Our World, a program that promotes less toxic pest control. According to the group’s literature on DEET-based repellents, fewer than 50 cases of serious toxic effects have been documented in the medical literature over 40 years of use. Some other repellents, such as lemon/eucalyptus oil or soybean, coconut and geranium oil, are as effective as a low-level DEET repellent that may last for three to four hours.

Pesticides, citronella, wrist bands and ultrasonic devices are not recommended mosquito deterrents. Electric bug zappers are costly, unsightly and likely to kill more good bugs than mosquitoes. And they don’t kill the larvae.

Go for the source. Kill the larvae before they have a chance to become mosquitoes.

No standing water means no mosquitoes.

Napa County Master Gardeners answer questions Monday, Wednesday and Friday,      9 a.m. to noon, at the U. C. Cooperative Extension office, 1710 Soscol Ave., Suite 4, Napa, 253-4221 or (877) 279-3065. E-mail garden questions by following the guidelines on the Web site, http://cenapa.ucdavis.edu.