Each weekday, our staff is busy monitoring the adult mosquito population throughout the county. We do this in many ways. One way is by setting specialized traps called light traps at designated sites county-wide. These traps are light sensitive and are activated at night because this is when mosquitoes are most active. The traps are collected the following morning and taken to our laboratory for identification. We identify and count every mosquito in each trap to get an idea of the population found in that area. When the trap sample reaches a state specified threshold, we are able to schedule a treatment called adulticiding. It is important to know what kind of mosquito is present in order to plan the most effective treatment.
Another way we monitor mosquito populations is by performing landing rate counts. They are taken at set sites each weekday at about the same time in the early morning. A landing rate count is done by going into areas where mosquitoes may like to hang out, rustling the surrounding vegetation, and counting how many mosquitoes land from the waist down in one minute. When the number of mosquitoes landing in one minute reaches a state specified threshold, we are able to schedule treatment.
Occasionally, a citizen will request one of our Inspectors to check a certain area. We will then perform landing rate counts on that site, as well as look for any possible breeding sites in the area that may be causing the problem.
During the mosquito season, our staff checks our sentinel chickens weekly for any mosquito-borne disease activity. We are specifically checking for St. Louis Encephalitis (SLE), Eastern Equine Encephalitis (EEE) and West Nile Virus (WNV), common diseases in the state of Florida. If viral levels for a flock are high, we may also schedule a treatment.
Once the state specified guidelines for adulticide treatment are met, we are able to schedule treatment. We have two choices for adulticiding. We are able to perform adulticiding treatment either by truck or by aircraft. The threshold for aerial treatment is much higher than that for ground treatment. The chemicals we use are chosen specifically for the type of mosquito found in the area to be treated. We do this because some chemicals are more effective on certain mosquito species than others.
The chemical is sprayed at high pressures creating a spray that is called ultra-low volume or ULV. This is beneficial because the droplets of chemical are very small. Being very small allows the chemical droplet to stay in the air longer and increase the droplet’s chance of hitting the target, a mosquito.
Because it is very small, the chemical droplet can easily be effected by wind, rain, and temperature. This is why we are only able to treat on relatively still, rain-free nights when temperatures are moderate.
When choosing the method of treatment (either by ground or by air), we not only take into consideration the size of the sample population, but also where the treatment is to be performed. If the area is difficult to treat with trucks, we may opt for an aerial treatment. If the area is easily treated by truck, we may opt for ground treatment.