Mosquito Control – Walter’s Thoughts

Summer rains can cause a population explosion of mosquitoes! Two kinds of mosquitoes are commonly seen (and felt!): the “swamp” or “Egyptian” mosquito, which feeds at dusk and the Asian tiger mosquito, which feeds during the day. The tiger mosquito has tiny white bands around its rear legs. Since the tiger mosquito flies and feeds during the day, it is the one that causes the most distress to gardeners and others who enjoy being outdoors.

Although they can be blown into your yard by the wind, it is likely that the mosquito biting you has come from just a few yards away! Adult mosquitoes lay eggs in damp soil or rotting vegetation. The eggs remain dormant until rain saturates the area. A small, hidden pool of water that remains for ten days may produce hundreds of ravenous pests.

Many people have seen the fogging trucks which operate at dusk in communities along the coast of Georgia. The insecticide fog stays close to the ground and kills most of the night feeding swamp mosquitoes. Unfortunately, it is VERY difficult to control Asian tiger mosquitoes with insecticides. Since these blood-suckers feed during the day, fogs and sprays are quickly dispersed by the wind.

Mosquitoes are best controlled by eliminating their breeding grounds. Females lay their eggs in batches of 50-200 directly in water or in areas that will flood later. Eggs may remain dormant for many months and then hatch within minutes after being flooded by a spring or summer rain.

NO STANDING WATER The BEST first step for either type of mosquito is to look for pockets of water outdoors and drain them. No water = no mosquitoes: it’s that simple. An organized search among neighbors may turn up dozens of mosquito hiding places. Look for clogged gutters, leaf-filled drains, drain outlets from air-conditioners, plastic wading pools, dog dishes, soft drink cans, plastic bags, old tires, “junk” behind the garage, birdbaths, potted plant saucers, standing water in tire ruts, stumps, tree holes, puddles hidden under English ivy and pools left by flooded streams.

TREAT PUDDLES If a pool of water can’t be permanently drained, i.e. bird baths and landscape water features, a special organic mosquito control can be used. The mosquito disease spore Bacillus thuringensis (B.t.) is sold at garden centers. A common brand name is Mosquito Dunks (click for sources). These can be put in pools of standing water, where they provide control for several weeks. This product is organically safe and can be used in birdbaths and around pets. Be sure to follow the directions on the label of any product that you use.

Examine standing water weekly to make sure that there are not mosquito larvae present. Dip out some water with a white styrofoam cup and look for the moving black specks that are larvae.

REPELLENTS Sometimes the best you can do is to station cans of mosquito repellent spray near the garden, lawn and deck. Questions have arisen concerning the safety of the repellent chemical so avoid heavy application to your skin. Lightly spray exposed flesh plus sock tops, pants cuffs and t-shirt collars. A product containing 35 percent DEET (click for sources) is sufficient for adults. Use 10 percent sprays on children.

I have been very pleased with products that contain Picaridin (click for sources). It does not have the greasy feel of DEET.

New repellents containing oil of lemon eucalyptus (click for sources) are also effective.


I am unequivocally opposed to mosquito misting systems. No matter what insecticide is used and no matter what timing is scheduled, mist systems harm beneficial insects. On balance, beneficials outweigh mosquito bites.

Read the comments of entomologist Dr. Paul Guillebeau


ULTRASONICS The copywriter who dreamed up the ad for the “ultrasonic mosquito repeller” deserves a special reward. A kick in the pants from the thousands who have bought the useless devices that “generate the sound of the mosquito-dreaded dragonfly” would be appropriate. Mosquitoes do not have ears. They do not hear train whistles, 747’s or approaching dragonfly wings. The only use I have found for these gadgets is once when I managed to kill two mosquitoes simultaneously by slapping my arm with it.

GARLIC From spook-repeller to heart medicine, garlic seems to be the cure for what ails you. Unfortunately, when subjected to scientific investigation, garlic has yet to show any mosquito repellency. Sure, some folks swear by it: “I take a garlic pill every day and I never get bit!” But perhaps the same claim could be made for the garlic preventing annoying phone calls that day. No convincing evidence has shown that garlic has any effect on mosquitoes.

CITROSA PLANT In recent years, ads fora mosquito-repellent citrosa plant has appeared. The citrosa is actually a scented geranium. Many plant oils are somewhat repellent to insects – the herb lemon balm actually contains more citronellal oil than the citrosa does. If you rub the plant leaves on your skin, insects will be kept away for a short time. One experimenter estimated plant oils to be 40 – 60 percent as effective as DEET, the active ingredient in most mosquito sprays. If you depend on the citrosa plant to keep mosquitoes away from your patio, the results may be much less than you desire. The citrosa is grown as an annual in Atlanta. It may be perennial in places where frost is rare.


CITRONELLA SMOKE Citronella can reduce the number of bites – but only for people who stand very close to the candle or Tiki torch. If you enjoy smelling like smoke and risking a clothes fire, smoke-generating mosquito products might be for you.

BUG ZAPPERS It is a macabre pleasure to listen to insects frying in an electronic bug killer. However, the bugs who meet their death are usually not mosquitoes. Entomologists found that 90 percent of the zapped insects were beneficial or harmless creatures which normally are eaten by birds in your yard. The choice of having fewer songbirds versus having a negligible effect on biting bugs seems easy to make. A recent report also raises the specter of germs being spread when insects are vaporized. Those “Ka-zzzzzzts” you hear in your zapper might be the sound of deadly germ bomblets being exploded. Not many people would picnic downwind of a zapper if they could see the germs that are deposited nearby.


It’s fun to empty a bag full of dead mosquitoes from these machines but they are not as effective as claimed. See Mosquito Traps – University of Florida


SKIN LOTIONS Lotions that contain citronella and other plant oils do repel mosquitoes. The question, though, is their effectiveness compared to other products. DEET (the active chemical in many mosquito sprays) is very effective when sprayed lightly on the skin. Bath oils and other lotions range in effectiveness from 10 percent to 80 percent as good as DEET.

FOGGERS Temporary relief outdoors can be had by using a fogger (not a garden sprayer) made specifically for mosquito control. A special insecticide will be sold for use with the fogger. Use it a few hours before an outdoor activity is planned. It will not be very effective on a windy day.


Insect Repellents

mosquito NCSU

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