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Spray Information

To find your spray block number, enter your address in the search box below. You can also browse spray blocks by visiting County Mapper.


The following spray blocks are scheduled to be sprayed:



The following spray blocks were sprayed last season:

​Date​Spray Block
​July 12, 2016​83
​July 13, 2016​67, 68
​July 15, 2016​​54, 55, 56, 57, 58
​​August 1, 2016​27, 70, 72, 73, 74
​August 16, 2016​83
​August 17, 2016​53 (partial), 105 (partial)
​August 26, 2016​106, 107 (partial)
​September 1, 2016​53
​September 13, 2016​83
​September 20, 2016​​72, 73, 74
​September 27, 2016​52, 53, 99


Telephone Hotline

To hear recorded updates, call 703-PWC-INFO (703-792-4636), then press '4', then '3'. This hotline is updated weekdays after 4 p.m. during the spray season.



Gypsy Moth ControlThe Prince William County Mosquito & Forest Pest Management Branch typically sprays for adult mosquitos Monday through Friday throughout the mosquito season, and spray (adulticide) is often done at night but can also occur during the daytime. There is no set schedule or order in which the blocks are sprayed. Rather, there are criteria established by the branch that trigger mosquito spray in a given area or neighborhood.

One trigger that could result in mosquito spray is based on surveillance trapping of adult mosquitos. If a threshold number of female mosquitoes is met or exceeded on a given night, this can trigger mosquito spray for that trap area. Another trigger for mosquito spray is that the mosquitos caught in a trap area test positive for West Nile Virus. For information on the Zika virus, click here.

The ideal or most efficient form of mosquito control includes treating or larviciding immature mosquitos in standing water.

Mosquito SprayingAdult mosquito spray is limited in its affect on adult mosquitos. The spray only affects adult mosquitos that are out flying and come into contact with the spray at the moment it is being sprayed. The spray does not affect mosquitos that are not active, at rest at night, or do not come into contact with the spray.

One of the most numerous and problematic mosquito species in Prince William County is not affected by spray, since it is inactive, or at rest during the evening and nighttime hours. That species is the Asian Tiger Mosquito. This species is among several found in the County that breeds in artificial or man-made containers, and is extremely difficult to control. You can help eliminate Asian Tiger Mosquitos by making sure containers that hold a tablespoon or more of water are emptied or flushed out at least once a week.


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