Our insecticides have no real residual effect. We must actually hit the mosquito directly with a droplet in order to kill it. If more mosquitoes fly into an area after the spray has settled, they are not effected. Obviously, it is very important to spray the right place at the right time under the right weather conditions in order to achieve control. It is very frustrating and expensive when large populations of mosquitoes are rapidly re-infesting residential areas, as repeated sprays are required. Spray trucks are sufficient for light mosquito populations, but aircraft are needed for moderate to heavy infestations and covering large areas quickly.
Surveillance
This is the key to the control program. We must spray only where needed and when needed in order to contact the maximum number of mosquitoes with the droplets. Surveillance methods used include mosquito traps, take landing rates (count the number that lands on you from the waist down in three minutes at different locations in the county), and considering citizen service requests when planning control efforts. We must have enough mosquitoes in an area to justify expense of control activity, as the cost to put an aircraft up with a load of chemical is approximately $4300. We can cover 4,000 acres with that one flight.
Basic Mosquito Biology
We have approximately 50 species of mosquitoes in Chambers County. Of these, the public commonly encounters about 12. It is important to know which species you are dealing with before control strategies can be planned and initiated, as the different species vary in breeding sites, flight ranges, peak activity periods, and biting behavior.
Eggs are laid in one of two ways, depending on the species. Some species (pool breeders) lay eggs directly on standing water. These eggs hatch in 24 to 48 hours, and the mosquito larvae take 5 to 7 days to emerge as adults. Fresh eggs are laid every day, so mosquito production is constant unless the water evaporates. This type of egg-laying behavior is also common in artificial containers such as tires, bird baths, buckets and cans, rain gutters, etc. These species usually fly only 1 to 5 miles.
Other species (floodwater breeders) lay eggs on dry ground in depressions or low areas that will hold water after a rain or high tide. These eggs are viable for several years and will hatch in minutes after being submerged if water temperatures are in the right range. Again, 5 to 7 days are spent in the larval stage before the mosquito emerges as an adult. Because all the eggs hatch at once, large numbers of mosquitoes are produced simultaneously. Think of them as tiny time bombs! This is why you have no mosquitoes on one day, and the next day you are covered with them. These species can fly up to 100+ miles. Some species also lay these eggs in dry artificial containers.
Regardless of the species, only 20% of the eggs that are deposited survive to become adults, and of these, about half, or 10%, are females. This means that only 10% of the potential mosquito population causes all of our problems.
Rice Field Mosquitoes
These are a large black mosquito with white or yellow bands on their legs. They are a flood water variety, with an average flight range is 20 to 40 miles. They are very aggressive biters, both day and night. The eggs are deposited in rice fields, fallow fields, & pastures in any depression that will hold water, including hoof prints. These mosquitoes are attracted to Chambers County and other areas in the gulf coast by the glow of lights at night, which can be found in any area of the county. We try to intercept these mosquitoes as they migrate in. Residents can do nothing to help us control this species.
Salt Marsh Mosquitoes
These are medium sized brown mosquito with white bands on their legs. Also a flood water variety, they are very aggressive biters with a flight range of 100+ miles. This species is most common in the eastern and southern areas of the county, and is attracted to town by city and industrial lights. Again, we try to intercept them on the edge of town as they move in. The public, again, can do nothing to help.
Asian Tiger Mosquitoes
Although first discovered in this country in 1985 in Houston, Texas, this species has become the #1 urban mosquito in the south. This is a small black mosquito with silver or white bands on the legs and one white stripe down the back between the wings. It lays eggs only in containers, not in puddles on the ground. Breeding sites for this species were originally in tree rot holes and stumps, but it now takes extensive advantage of the artificial containers that we so thoughtfully provide (cans, buckets, tires, bird baths, clogged rain gutters, pet water dishes, anything that will hold water for 5 to 7 days). Eggs are laid just above the water line in the container. Rain fall or movement of the container submerges the eggs, which hatch in minutes. Peak activity period for this mosquito is rather unusual, being during middle of the day instead of at night. The flight range for this mosquito only 1 to 2 miles, so if you breed them, you will feed them. They are hesitant but persistent in biting behavior. This species receives only minimal exposure to our sprays due to the unusual daytime activity period. The only effective control for this mosquito is removal of the breeding sites by property owner. The public must help with this one.
Culex Species
These are small, nondescript brown mosquitoes, most of which are active only at night. They breed in standing water high in organic matter, and are common in underground storm sewers and in water standing under houses built on piers. They have only a 1 to 5 mile flight range. One species can transmit St Louis Encephalitis if it bites an infected bird and then bites a human. Residents can help by eliminating water standing around the home.
Mosquito Trivia
Mosquitoes cannot transmit AIDS.
Purple martins and bats may eat a few mosquitoes, in fact, we count on their help, but they will not cause a noticeable drop in your mosquito population.
Only female mosquitoes bite. Blood supplies proteins to build eggs with, rather than being a food source. Mosquitoes live on carbohydrate sources like nectar and plant sap. They have even been known to sneak a little sugar water from hummingbird feeders.