Pike's Pick

Georgia Gardener Newsletter Design Tip: May 28, 2009

Mosquito Control

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Donut-like larvicide kills developing mosquitoes

Let me start by saying that I'm not an entomologist, but like most of you, I'm a frequent mosquito victim. Since my work keeps me outdoors so much of the time, I can attest to the fact that I've sustained mosquito bites from early March to late November when warm weather was early or late. During the last few years of drought, I've noticed a decline in the number of mosquito bites but with this year's return of the rain, I've been under constant assault since late March.

To understand how to control mosquitoes it's important to understand their life cycle. There are unbelievably 63 or more species of mosquito in at least 12 genera found in Georgia! Over the last two decades, I've noticed a decline in the more common native species in and around most Georgia metropolitan areas. These native species were the ones from our childhood where they would be active in the early morning and evening hours and would lay their eggs in water-filled areas (including natural areas). More recently, these mosquitoes seem to have been replaced by the Asian Tiger Mosquito which prefers to lay its eggs in water-filled areas created by man and is on the prowl all day long.

Female mosquitoes are the only ones that bite. They obtain blood from a variety of creatures that they use to feed their developing eggs. Eggs are laid in standing fresh (sometimes brackish) water from which they develop into the tiny "wigglers" often seen floating near the surface. An adult Asian Tiger Mosquito takes 10-14 days to go from egg to larva to pupa to adult. Asian Tiger Mosquitoes overwinter in the egg stage and hatch when rainfall and temperature conditions are favorable.

Adult Protection & Control: What Works, What Doesn't

To effectively control mosquitoes, it's important to protect yourself from the adult females as well as preventing the completion of their life cycle from egg to adult. There are a number of organic and synthetic pesticides that can be used on mosquitoes during their life cycle, some better than others.

Adult female mosquitoes are attracted to dark clothing, perspiration and carbon dioxide. When outdoors, wear light-colored clothing, long sleeves and pants, gloves and a hat. Stay away from dark, damp areas during certain times of the day. Personal observation has taught me that mosquitoes are more active when the humidity is high or it has recently rained. Using insect repellents that contain DEET (N,N-Diethyl-meta-toluamide) work well for me but some people are reluctant to use such synthetic products. By confining the application of repellents to the clothing, I have been able to greatly reduce my exposure to such chemicals. Oils from certain herbs seem to have repellent characteristics and I can attest that rubbing rosemary on my skin seems to help greatly.

When lounging outdoors, the use of a fan can keep mosquitoes from finding your carbon dioxide and perspiration "scent." I'm not all that convinced of the effectiveness of citronella candles as the protective area seems to be very limited. Ultrasonic devices have not been proven effective by reputable research that I can find. I've tried these products and they did not work for me at all. Ditto that on zappers that use carbon dioxide.

As for controling adult mosquitoes in the landscape, there are effective pesticides but I'm generally opposed to the broad application of these products for several reasons and I'm STRONGLY opposed to the various automatic misting systems that can be installed to spray pesticides on a regular basis. These products do more harm than good. Let me repeat, these products do more harm than good.

As I said before, I'm not an entomologist, so when it comes to making such comments, I defer to the experts. Dr. Paul Guillebeau, Professor of Entomology at UGA, makes some strong comments on these systems which can be read here.

Immature Mosquito Control and Where They Lurk

The pre-adult stages of a mosquito's life are spent in standing water. Remove the water or somehow treat it and you can prevent the immature mosquitoes from reaching adulthood. I'm always surprised at how little water it takes to grow a crop of mosquitoes - less than a teaspoon. Just think how many teaspoon-sized "puddles" of water are hiding in your landscape, especially with all the rain we've had.

Check your landscape every few days for water standing in these locations: catch pans for outdoor plants, pet dishes, birdbaths, non-circulating ponds, trash cans, garbage, old tires, tree stumps, clogged gutters and downspouts, corrugated downspout tubing, buckets, rainbarrels, thick plantings (especially English ivy), culverts/drainage ditches, puddles adjacent to creeks and on and on and on.


Water collecting in the bottom of corrugated tubing	English ivy as a home for developing mosquitoes

Routinely empty containers that collect water and for those that can't be emptied, such as ditches or lingering puddles, toss the donut-shaped larvicides into the water. These products contain biological agents that specifically target mosquito larvae/pupae and are harmless to other creatures. Read the instructions on the amount and frequency that these products should be used. Of course, keep in mind, these larvicide products won't affect adult mosquitoes. For that, you're back to protecting yourself.