Mosquito Control

Rebecca Brandt, Manager

810 Livingston Avenue
Bay City, Michigan 48708-6380
Voice: (989) 894-4555
Fax: (989) 894-0526

Controlling Mosquitoes

In order to accomplish long-range and environmentally sound mosquito control, an Integrated Mosquito Management (IMM) approach is incorporated, which uses many control methods including surveillance, breeding source reduction, biological control, chemical control, and education.

Larval Mosquito Control

Larviciding, or controlling the mosquito in its larval stage, is the most effective control method because larvae are concentrated in a relatively small area. 

The program uses a variety of equipment when larviciding.  Small sites may be treated using a Spyker® spreader to apply granular material or a hand-operated Hudson® pressurized spray tank to apply liquid control material.  Truck-mounted equipment such as the liquid larval unit is used to treat ditches that are breeding larvae throughout the county.  Large flooded woodlots are treated using airplanes in the spring.  Spring Aedes mosquitoes hatch en-masse in mid-March and develop in woodland pools where they emerge as biting adults in mid-May.

Technicians are assigned a township or township section(s) and given a set of maps or descriptions of known habitats contained therein.  Technicians visit sites, use a standard pint-sized dipper as a tool to locate larvae and/or pupae, collect samples for later identification, record data on an inspection form, dump water if possible, or apply the appropriate control material to kill the immature mosquitoes.  Daily records and weekly summaries are kept for all larviciding activities.

Primarily, Bay County Mosquito Control uses a bacterial product, Bti (or Bacillus thuringiensis israelensis) to control larvae.  Bti is very effective against mosquito larvae and can be used as a food source for other aquatic organisms in the breeding site.  Another granular larvicide and bacterium is Bacillus sphaericus (Bs).  This product is like Bti in that the larva must ingest it in order to be effective.  Unlike Bti, however, Bs is a live bacterium that, once ingested, will replicate (reproduce), which creates more product residue in the water for a longer control window.  Another larval control product, Natular, contains a naturally-occurring soil bacterium, spinosad.  Natular is available in six formulations and all domestic formulations are also made with inert ingredients that are on the EPA Minimal Risk List.  Furthermore, Natular is the first larvicide evaluated as a Reduced Risk product by the EPA.  For more information about Natular, visit the manufacturer's website listed below:

Another granular larvicide is temephos, which is used to control mosquito species that are not susceptible to Bti.  Temephos is also used to control early instars (young larvae) that are not yet actively eating, as temephos is a contact insecticide. 

Larvicide oils are also used when mosquitoes have reached the pupa stage.

Adult Mosquito Control

Although 70% of our control efforts are aimed at the larval stage, adult mosquito control will always be a supplemental part of the program.  Adulticiding, or controlling the mosquito in its adult stage, is initiated based on a confirmed need through adult mosquito surveillance (light traps, CDC traps, gravid traps) and, secondarily, service requests from Bay County citizens.  Spraying adult mosquitoes is also necessary when mosquito-borne diseases have been detected in adult mosquitoes.

Control measures are initiated using ULV (Ultra Low Volume) spray equipment, which allows minimal amounts of insecticide to be used.  The very small droplets that are produced (10-17 microns in diameter) drift through the air to contact flying mosquitoes.  Insects that are not active during twilight and evening hours will not be affected by the spray, as there is no significant residue left in the environment.  The use of adulticides is governed by density of mosquitoes in an area and by weather conditions such as temperature, wind speed, and wind direction.Permethrin products are the adulticides used to control mosquitoes.  The idea behind the ULV fogging program is to keep residential and recreational areas reasonably free of biting mosquitoes.  Our goal is not to eradicate mosquitoes, but to reduct their numbers.

Maintaining courteous and responsive customer relations is an important part of our mosquito control program.  Complaint calls are used as one of several indicators of where mosquitoes are creating annoyance problems.  Citizen calls help us to target problem areas with both larval and adult mosquito control.

Public Education

Public Education efforts are handled through printed materials (brochures, door hangers, pamphlets), school visits, enhanced web page links, and public service announcements.  Press releases are distributed to the media, government officials, and posted here on the Bay County web site, as needed.

Source reduction to eliminate mosquito-breeding habitats is the most vital course homeowners can take to reduce the number of mosquitoes in their backyard.  It is important to remember that homeowners can do their part to eliminate mosquito breeding by following a few simple rules at home, including changing the water in bird baths every few days, dumping water from containers, and bringing scrap tires to our annual scrap tire drive.

Source Reduction

Source reduction, the permanent removal of breeding sources, is accomplished in part through a residential tire drive.  Typically, one tire drive will be held during the summer months.  Each county residence may dispose of up to 10 passenger car or pick-up tires at no charge.  Semi and tractor tires are not accepted.