Mosquito Control Policy

The Maryland Department of Agriculture (Department) provides mosquito control services, in cooperation with participating county governments, as authorized by State law. The Department's preferred mosquito control strategy is the reduction of mosquito larvae numbers by source reduction, biological control agents or use of biological insecticides. Adult mosquito control, by ultra low volume (ULV) application of insecticide, is conducted using aircraft or truck-mounted application equipment in residential areas for nuisance abatement and to protect public health from mosquito-borne disease.

Adult Mosquito Nuisance Control

MDA recognizes that the annoyance caused by moderate to large numbers of mosquitoes can adversely impact the quality of life for citizens and visitors in Maryland. Control of populations of nuisance mosquitoes in residential areas will be conducted in accordance with this policy.

Nuisance mosquito control will be provided only in residential areas (cities, towns, communities, individual residences) that specifically request mosquito control service and that cost-share to fund conduct of the program.

The adult mosquito population must meet, or exceed, a minimum density to justify the application of pesticide. Two measurements of adult mosquito density are used in Maryland: (1) landing rate counts, and (2) light traps.

The minimum landing rate threshold to initiate spraying of insecticide with ULV ground application equipment is 3 mosquitoes landing on an inspector in a 2-minute period. The minimum light trap collection to warrant ground spraying is 12 female mosquitoes, of a species known to feed on humans, per night.

The minimum action thresholds for aerial application of an insecticide for nuisance adult mosquito control are: (1) an average landing rate count of 12 mosquitoes per minute; or (2) a light trap collection of 100 female mosquitoes per night.

It is preferred that landing rate and light trap criteria be used to evaluate the need for application of an insecticide. However, either method alone can be used. Aerial or ground spraying for adult mosquitoes will be done only when the minimum action threshold for landing rate counts or light trap collections is met or exceeded. The mosquito surveillance data must have been collected in the vicinity of the proposed treatment area within 48 hours prior to the treatment date. Service requests, i.e., complaints, from communities participating in mosquito control efforts do not provide sufficient justification for nuisance adult mosquito control. However, service requests will result in increased mosquito surveillance by mosquito control staff. An inspector will respond to a service request within two (2) business days after the request is received.

Exclusions of Property from Nuisance Adult Mosquito Control Spraying

An individual may have their owned or leased property excluded from nuisance mosquito control. This exclusion will include a buffer of approximately 300 feet around the property. Each individual requesting this exclusion must submit the request in writing to the Department and provide a copy to the appropriate city, town, or county government. The individual may also notify the appropriate community association. The request must include the address of the property to be excluded from spraying and must be signed by the owner(s) or lessee(s). Annual updates are required of requests for exclusion from spraying. Download the Mosquito Control Exemption Form to opt into the exclusion.

If the number of individual objectors and/or the location of the excluded property precludes an effective mosquito control adulticide service for a community, the service will be suspended. Adult mosquito control service may be reinstated to the community upon written request to the Department from the community association, town, city or county, if continuation of the mosquito control service is determined by the local authority to be in the best interest of the public. Because it is a cooperative program, the Department will defer to the local authority for the final decision relating to property exclusion policy. All disputes regarding this issue will be settled by the local authority. After service reinstatement, the Department will notify the individual who had requested the exclusion about the decision to reinstate service. The Department may attempt to exclude the application of insecticide immediately adjacent to the property of the person(s) requesting the exclusion, but will not provide a buffer around the property.

Adult Mosquito Control to Protect Public Health from Mosquito-Borne Disease

West Nile encephalitis, eastern equine encephalitis, St. Louis encephalitis and Zika virus are mosquito-borne diseases that can adversely impact human health in Maryland. If any mosquito-borne disease becomes a real or imminent public health threat, adult mosquito control will be a priority issue. Under such conditions, spray exclusion zones will not be recognized and the action thresholds may be lowered. The department will exercise all means possible to reduce the adult mosquito population to the lowest level possible within the area where disease transmission to humans is a concern.