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Aerial Adulticide FAQ

Why is aerial spraying taking place? 
The District conducts aerial spraying based on surveillance indicating high mosquito activity or disease transmission within an area. Aerial spraying can help by reducing the number of infected adult mosquitoes which will reduce the risk of disease transmission to people. In addition, mosquitoes are exhibiting resistance to pyrethrins/pyrethoids, so utilizing aerial applications of organophosphate products allows us to effectively manage these resistant populations.For more information on our surveillance program please click here: TMAD Surveillance
What types of insecticides are used in aerial applications? 

Adult mosquito control is always a last resort. The District strives to control mosquitoes in the larval stage before they disperse as adults; however, this is not always possible. When surveillance indicates high mosquito populations and/or disease activity, then ground and/or aerial adulticiding may be utilized. Currently, the organophosphate naled (Trumpet EC/Dibrom) is being used by the District as an aerial adulticide.

Trumpet EC/Dibrom are approved organophosphate products which are synthetic, organic pesticides that contain carbon, hydrogen, and phosphorus and act by inhibiting the enzyme cholinesterase in insects.

These products are applied at .8 oz per acre. (That is roughly 1 1/2 tablespoons over a football field.)

When are mosquito control applications made? 


Generally, applications are made early in the morning, evening or nighttime hours when mosquito species are most active. This is also when the winds are calm and the most effective insecticide application can be made.

How can I find out if Spraying is taking place in my area? 


Residents are encouraged to sign up for spray notifications to receive information on treatments occurring in their area. There are 3 notification options:

When do spraying notifications get posted? 
Generally, the notifications will be posted 24 to 48 hours in advance of applications. Treatments may be canceled and rescheduled due to weather conditions or other unforeseen reasons.
Why can I see and hear the plane if I am not within the treatment area? 


The plane is equipped with specialized tracking equipment which is sensitive to current weather conditions. The equipment measures wind speed, direction, humidity, and temperature. The equipment is able to determine what flight adjustments the plane needs to make, to place the spray in the targeted area. This means that sometimes the weather conditions may require the plane to fly offset from the target area.

Is it safe to be outside when the applications are made? 
We encourage you to check for notifications of applications in your area. The applications should not pose a significant risk to you or your family; however, people who may suffer from chemical sensitivity may want to remain indoors and keep windows and doors closed during the application. Generally, there is no spray in the air 15 minutes after the application equipment has left the area. The material degrades rapidly in the environment and should not interfere with normal outside activities.
What steps should I take to reduce exposure during spraying? 

There is no need for individuals to take any other special precautionary measures during mosquito control spraying. However, people with chemical sensitivity may want to remain indoors and take the following steps:

  • Close windows and doors. Turn off a window mounted AC. Generally, there is no material left in the air 15 minutes after the application equipment has gone out of the area.
Can pets go outside during spraying? 
The materials used for controlling mosquitoes pose minimal risk to animals when used in accordance with the pesticide label. However, if you want to reduce your pet‘s exposure, keep them inside during the application. Naled, the active ingredient in Dibrom and Trumpet EC, degrades rapidly in the environment. In most cases, it is not possible to detect any residue within 1 to 2 hours.
Should I turn off my air conditioner if spraying is scheduled in my area? 
There is typically no need for any special precautionary measures during mosquito control spraying. However, as mentioned above, people who suffer from chemical sensitivity may want to close doors and windows and turn off any window mounted AC units. Since a central air-conditioning unit does not pull in outside air (recirculates interior air), there is no need to turn these units off at all.
Where can I get additional information regarding specific insecticides? 
Questions concerning specific insecticides can be directed to the U.S. Environmental Protection Agency, as this agency has responsibility for registration of insecticides. Many issues are addressed on the EPA‘s Mosquito Control Web site.

The National Pesticide Information Center (NPIC) provides insecticide information and questions about the impact of insecticide use on human health. NPIC is cooperatively sponsored by Oregon State University and the U.S. Environmental Protection Agency. NPIC can be reached online or toll-free: 1-800-858-7378.

For more information on ground adulticides please click here: Ground Treatment

Adulticiding Maps

Grayson and River RdGreater CeresGreater GraysonGreater HughsonHickmanHills FerryKeyesLas Palmas STNewmanSouth ModestoSouthern StanislausTurlock/Denair