Information on Adulticiding

June 13, 2011

As a reminder the adulticiding (fogging) schedule will be posted under the “Adulticiding Schedule” heading on this website.

Please take some time and walk around your yards and or property to check for any standing water.  This can be water in cans, tires, planters , etc.  mosquitoes THRIVE in these areas and MUST have water to lay their eggs in.  We appreciate you doing your part in controlling the mosquitoes/larva in your area.



June 13, 2011

Decades of testing and field use demonstrate that the larvicides used by the Districts are safe for people and for the environment.  They have high selectivity and low toxicity to non-target organisms, are applied in low concentrations and have low persistence resulting in no potential significant post-application residues.  They are generally recognized as the “least toxic” of the effective available materials (Figure 1).  They are used in small quantities as a portion of highly regulated IPM programs and their application rates are sufficiently low to leave the physical parameters of the environment (i.e., temperature, salinity, turbidity and pH) unchanged.

All of the materials currently in routine use by the Districts can be considered “less toxic” or “least toxic” according to US EPA acute toxicity data (Fig. 1).

Fig. 1.  Relative toxicities of pesticides used by mosquito and vector control programs based on rat LD50 data from product labels, in comparison with some common household chemicals. “Less toxic” or “least toxic” according to US EPA acute toxicity data (Fig. 1).


June 12, 2011

The mosquito season is in full swing.  We all know that mosquitoes love water and this year we have a lot of water.   We have high water in areas that are normally dry at this time of the year  and other areas that haven’t seen water levels like this in many years.  As a result we will start to have more mosquitoes move into our resident areas and town. As these numbers cross a certain threshold, the District will begin its adulticide program. By reducing the numbers of mosquitoes, the odds of being bitten diminish. More importantly, when disease is present, the chances for transmission are lowered.

Adulticiding must be done during a temperature inversion. During the mosquito season, temperature inversions typically occur at dawn and dusk. So fogging is either done in the late evening, after 9:00pm or early in the morning before most people are awake or active outdoors.

Mosquito activity peaks at both dawn and dusk. Fogging at one of these times allows for the best chance of impacting mosquitoes while decreasing the chances for an exposure in people.

The District posts the fogging schedule each week on the website so residents can be aware of spray operations. Residents are encouraged to avoid sprays by staying indoors and by keeping doors and windows closed between the hours of 9:00 PM and 6:30 AM.

While adulticiding can be an effective tool and generally provides a certain level of control in a timely manner, it is susceptible to a number of factors. Wind speed (too high), temperatures (too cold or too hot), access (being able to physically drive to areas where the mosquitoes are located) and timing (maximizing mosquito exposure while minimizing exposure to people, pets, etc) are all considerations that can affect the performance of adulticiding. Consequently, these and other factors may prevent us from performing an adulticiding event on the night and in the location that we have listed below.