Mosquito Control

Rebecca Brandt, Manager

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

Controlling Mosquitoes

Bay County Mosquito Control manages mosquitoes using an Integrated Mosquito Management (IMM) approach, which means using a combination of techniques to control mosquitoes such as education, source reduction, larval control (the control of mosquitoes in the larval stage), and adult control (the control of mosquitoes in the adult stage) to reduce mosquito populations while minimizing risk to the environment.  Although efforts are geared toward limiting habitat available to mosquitoes through education and source reduction (dumping water from containers or covering them), it is sometimes necessary to manage mosquitoes in other ways. Read below for the multiple ways Mosquito Control performs treatments throughout Bay County:



Source Reduction and Public Education


Source reduction, the permanent removal of breeding sources, is the most vital course homeowners can take to prevent mosquitoes in their backyard. It is important to remember that homeowners can do their part to reduce mosquito breeding by eliminating sources of standing water 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. Typically, two tire drives are 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.

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





Larval Mosquito Control

Larval control is the term used to describe controlling mosquitoes in standing water while in the larval or pupal stage of development, before they emerge as adults. Larval control is the most effective method because larvae are concentrated in a relatively small area.  Virtually any natural or man-made collection of standing water can breed mosquitoes including ponds, flooded woodlots, flooded fields, drains, ditches, catch basins, containers, neglected swimming pools, etc. Nearly 70% of Bay County Mosquito Control's operations are spent controlling larvae, with over 15,000 breeding sites inspected annually. Approximately 10-15% of these sites require treatment with a control material. Larval control activities vary depending on the time of year.

SPRING AERIAL TREATMENT - Aerial treatment of seasonally flooded woodlots signals the beginning of the mosquito control season and over 50,000 acres are treated throughout Bay County in April. Only flooded woodlots are treated at this time since that is the only habitat that breeds the spring species of mosquitoes. The aerial operation targets larvae before they reach the adult, biting stage using a bacterial product known as Bti. The aerial program has been in place for over three decades in Bay County and remains the best way to dramatically decrease numbers of spring mosquitoes. Woodlots not part of the aerial program are treated by foot crews.

SUMMER LARVAL CONTROL - Technicians conduct daily mosquito surveillance in a variety of aquatic habitats. These sites include backyard inspections of pools, containers, and ponds and other more permanent habitats like ditches, flooded fields, woodlots, and marshes. Other summer larval control operations include treatment of catch basins throughout Bay County, imperative in reducing the risk of Culex mosquitoes, a known disease vector. Catch basins can be found along streets, in parking lots, and in backyards. Each year at least 35,000 individual catch basins will be treated with naturally-occurring products. After major rainfall events, priority is given to treatment of roadside ditches throughout the County, a major habitat of floodwater mosquitoes. Thousands of miles of roadside ditch are also treated each year using truck-mounted units dispensing  biorational public health mosquito control products.

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 larval control product evaluated as a Reduced Risk product by the EPA. Bay County Mosquito Control also utilizes an insect growth regulator, S-Methoprene, for residual larval control. S-Methoprene acts as a juvenile insect hormone that prevents mosquito larva from maturing into biting adults.

When mosquitoes reach the pupal stage, bacterial formulations are not effective as those products require the mosquito to eat the product. Since the pupal stage is a non-feeding stage, larvicide oils, consisting of mainly mineral oil, are applied to the standing water causing suffocation of pupae.


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.  Adult mosquito control is the fogging of mosquitoes in the adult stage. It 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.  Fogging is an aerosol application of insecticide designed to control adult mosquitoes in flight.

Control measures are initiated using ULV (Ultra Low Volume) spray equipment with insecticides applied in very small amounts (less than 1 ounce of active ingredient per acre) which allows minimal amounts of product 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 adult control products is governed by density of mosquitoes in an area and by weather conditions such as temperature, wind speed, and wind direction.  Products with an active ingredient of permethrin are what is used in adult mosquito control.  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 reduce their numbers.

Fogging is performed by technicians certified by the State of Michigan and insecticides are applied in strict conformance with label requirements. Applications are conducted at night when mosquitoes are most active, beginning after sunset and ending around 1 a.m. Treatment areas vary each night as multiple factors such as trap counts, disease activity, rainfall data, and citizen requests assist in determining fogging routes. Typically, it takes three or four evenings to complete the treatment of an individual township as townships are made up of several spray routes that allow for efficient treatment application.

Product labels and Safety Data Sheets (SDS) can be found on the "Product Labels" link on the Mosquito Control home page. 

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.