Mosquito Control Methods

Breeding Areas & Control

York County has 43,000 acres of water, encompassing woodland pools and marshes coupled with many miles of drainage ditches that enable mosquito breeding. To protect the health and welfare of our citizens from potential mosquito borne diseases an Integrated Pest Management (IPM) Program is utilized.

Under the proper conditions mosquito populations can increase greatly. When this occurs, we endeavor to treat standing water with a biological insecticide. If mosquito populations continue to rise, spray trucks are dispatched in the evening when weather permits. When a serious mosquito infestation is imminent, arrangements may be made for an aerial spray flight.

All applications are undertaken by licensed personnel using only EPA registered insecticides. We strive to use the least toxic pesticides available for their prevention.

Drainage Maintenance

Drainage way maintenance is perhaps the most important component of our IPM Program. York County is proud to employ three ditch maintenance crews, each comprised of four workmen. Workloads for each crew are delegated by election district.

The crews aim to clear every County maintained ditch at least twice per year. Ditch maintenance work is difficult and is all done manually using hand operated equipment. Over 100 miles of ditches are manually cleared every year. The ditch crews are also instrumental in debris clean-up and removal in the event of a large storm event.

Biological Control


The Larval surveillance program for York County consists of three separate strategies.

Monitoring Permanent Bodies of Water
Permanent bodies of water (ponds and permanent marshes or swamps) normally have populations of predatory species (fish, amphibians and other insects) which prey on mosquito larvae. York County monitors all permanent bodies of water for presence of fish. Gambusia holbrooki (mosquitofish) will be added if needed.

Temporary Bodies of Water
Temporary bodies of water (low depressions, residual ditches or artificial containers) usually, unless they are vernal pools, have no natural predators for mosquito control. Mosquito control uses our extensive GIS mapping system to monitor areas of low depression for the purpose of larval control. Stormwater drainage crews also monitor and report sightings of larvae to mosquito control for larvicide treatment.

Filling Tree Holes
Locating and mapping tree holes has become an important issue for Mosquito control. Since tree holes fill with water and have to be treated every 30 days, Mosquito control has taken it upon themselves to locate tree holes and fill them with sand for a more permanent solution to mosquito larval habitat.

Larviciding Products
The products used for larviciding in York County are specifically targeted against mosquito larvae. One of the products used is Bactimos Briquettes. This larvacide is a kitty-litter donut impregnated with a bacteria, Bacillus Thruingiensis variation Israelensis (BTi). The donut falls apart over time releasing the active ingredient.

When mosquito larvae eat this bacteria they become sick and die. This bacteria affects only mosquito larvae and its considered harmless enough to be used in drinking water. Mosquito dunks are provided to York County citizens free of charge and can be picked up at the Waste Management Center located at 145 Goodwin Neck Road, York Library and Tabb Library.

Package of mosquito dunks

Mosquito Fish

Natural Control Methods
York County is committed to using natural control methods to reduce reliance on pesticide spraying for mosquitoes. We've implemented an aggressive fish management program by stocking Gambusia holbrooki, aka "mosquito fish," in artificial impoundments, ditches, ornamental ponds, borrow pits and stormwater retention ponds, and other places where mosquitoes breed.

Mosquito fish

This tiny fish devours mosquito larvae, reducing the numbers of adult mosquitoes. Gambusia holbrooki are considered native to this region and are commonly found in tidal areas and streams. They are related to guppies, and like guppies they bear live young. They are a hardy fish able to tolerate winter, over-crowding, and poor water quality.

Request Mosquito Fish
If you reside in York County and are interested in adding mosquito fish to your ornamental pond any other area of permanent standing water, contact us at 757-890-3790 for an evaluation. Mosquito fish are provided free of charge.

If you reside outside of our jurisdiction, please contact your local mosquito control, extension agent, or Virginia Game and Inland fisheries for further information.

Mosquito Repellant Plants Guide

This guide contains information on plant species that have been shown to naturally repel mosquitoes.

Chemical Control


Adulticiding is the use of pesticide to control adult mosquitoes. This can be accomplished two ways, either by truck mounted equipment or by aircraft.

When a need is determined through our surveillance program, ground spray trucks will run Tuesday through Friday between 12 a.m.- 6 a.m. The pesticides used are Duet and Zenivex E4, delivered as an aerosol, and distributed at an average of 1.5 ounces per acre.

Spray trucking driving down street and spraying

Spray Exclusion
If you wish to exclude your property from ground spraying, please complete the Mosquito Spray Avoidance Request form.

Spray Season
During the spray season, typically May through October, spray information will be posted on our website.  Please call Mosquito Control at 757-890-3790 with any questions.

Aerial Spraying

When a need is determined, the County may be sprayed by aircraft. Spraying may be completed by the Air Force using a C-130 aircraft from the Air Force Reserve unit based in Youngstown, Ohio. For an Air Force flight, the pesticide used is Dibrom Concentrate delivered as an aerosol at 0.5 ounces per acre.

Alternately, spraying may be completed by Dynamic Aviation using specially equipped twin engine aircraft. For a Dynamic Aviation flight, the pesticide used is Duet delivered as an aerosol at a rate 0.41 ounces per acre.

Bee Precautions
At this dosage the insecticide is safe for humans and animals, but will sometimes kill non-target insects, such as honeybees, if not protected before the spray. For this reason beekeepers are urged to take precautions to protect their hives and to register their hive locations with York County Mosquito Control. Registered beekeepers will be individually notified at minimum 48 hours prior to an aerial spray.