Adult Mosquito Nuisance Control

Truck on a Road Spraying ChemicalsThe Department 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 the conduct of the program. The adult mosquito population must meet, or exceed, a minimum density to justify the application of pesticides. Two measurements of adult mosquito density are used in Maryland: 

  • Landing rate counts
  • 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: 

  • An average landing rate count of 12 mosquitoes per minute
  • 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 business days after the request is received.

Mosquito spraying is not harmful to honeybees according to the MDA. According to the MDA Mosquito Control Website.

We are very concerned about the effects of our activities on non-target organisms, like honeybees and bats. We only conduct truck mounted spraying or misting at night. Bees are not active at night. The droplets in the spray have an extremely small diameter. The surface to mass ratio of these droplets is such that these droplets do not leave residue on surfaces. They are like tiny parachutes. When they are pulled down by gravity, drag keeps them from falling. The point is that these droplets do not land or stick on surfaces. When bees become active the next day and crawl across surfaces, those surfaces do not have any pesticide from our spray. The droplet size averages 15 micrometers. There are 1000 micrometers in a millimeter. We must have our machines tested, by law, twice a year.