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Under the direction of the Superintendent and the Chief Inspector, a comprehensive surveillance and inspection program is operated to monitor mosquito populations. When necessary, staff members implement appropriate control measures. All mosquito control work is based on this monitoring system. There are 50 different types (species) of mosquitoes in Morris County, but only about 10 of these pose a nuisance or disease threat to residents.

An inspector uses a simple dipper is used to check for mosquito larvae.

An inspector uses a simple dipper is used to check for mosquito larvae.

There are a number of methods used to gauge mosquito population levels. To monitor the aquatic (larval) stage, a simple dipper is the tool of choice. Adult mosquito populations are tracked using a device called the New Jersey light trap, developed at Rutgers University in the 1930s and used world wide as a standard sampling tool. Service requests from residents are also important in identifying problems areas, but Division staff will perform landing counts (counting the number of mosquitoes biting in a set period of time) before any control measures are implemented. Portable dry ice baited traps are sometimes used in remote locations (mosquito females are attracted to carbon dioxide).

Since 2000, there has been a comprehensive monitoring, testing and control program in place to contain West Nile virus, a disease carried by the common House mosquito. West Nile virus was discovered in NYC in 1999 and has since caused illness in thousands and death in hundreds of people across the U.S.


Staffer from Morris County Mosquito Control sets a mosquito trap that uses dry ice as bait. The captured mosquitoes are identified and counted to determine the treatment method and severity of infestation.

A staffer from Morris County Mosquito Control sets a mosquito trap to identify and count mosquitoes to determine the treatment method and severity of infestation.

When surveillance indicates the need, control measures are used to reduce mosquito population levels. We act against the aquatic (larval) stage most frequently, and only control adult mosquitoes when they are extremely abundant. The product we use most often to control larvae is a soil bacteria that is grown commercially and applied either on corn cob granules or as a liquid. This biological product is specific for mosquitoes, and must be eaten by the larvae to act. Other organisms in the mosquito habitat are not harmed.

In certain areas, the mosquito fish, Gambusia affinis, provides suitable control. These fish are placed in compliance with all state and federal guidelines, and represent a biological approach to mosquito reduction.

If adult mosquitoes are abundant, or there is a threat of disease, we will apply insecticides by truck mounted sprayers. These materials are used at very low rates, in the ½ to 1 ounce per acre , and they break down quickly in the environment. Control of adult mosquitoes is a last resort, but is sometimes necessary. Again, this action is taken ONLY when surveillance shows there is a need.

Water Management

This is a critical, but often overlooked portion of a comprehensive mosquito control program. Without this work, however, mosquito populations would be much higher and there would be a much greater need to apply other mosquito control methods. This critical function is carried out all year long, partially answering the question, “what do you do in the winter time”?

Photo of streambed that feeds a small river

Our water management program is overseen by the General Supervisor and Wetlands Specialist. The crew is responsible for brush cutting, the removal of blockages, and hand restoration of drainage ditches. We also assist municipalities or other County agencies with tree removal provided they are creating a mosquito issue.

Restoration of ponds, storm retention facilities and drainage systems is often needed. Under the direction of the Wetlands Specialist and General Supervisor, appropriate environmental permits are obtained, projects are set up, and work is conducted. This work is done in a manner that helps draw off surface water but does not “drain” wetlands, thereby controlling mosquitoes without changing the basic nature of the habitat.

Most people are not aware of this very important portion of the mosquito control operations by the MCMEC. The end results, however, are lower numbers of mosquitoes and a reduction in the application of mosquito control products.

Lake before mosquito treatment

Lake after mosquito treatment

Education and Public Awareness

Fact sheets, posters, school poster contests, media contacts and formal presentations are all employed to let residents know what we do. This has taken on an even more critical role after the outbreak of West Nile virus.

This disease, carried by the common house mosquito, can be controlled to a large degree if residents remove objects that hold standing water around their homes. Download Controlling Mosquitoes Around the Home.