By Emily Schopfer
Mosquitoes collected in Middletown, Holmdel and surrounding municipalities tested positive for West Nile virus, prompting adult mosquito-control operations across parts of the area in late August and September.
Two rounds of insecticide spraying in Middletown began after an Aug. 19 announcement from the Monmouth County Board of County Commissioners, which said mosquitoes collected June 18 had tested positive for West Nile Virus. The county announced Monday that spraying would occur in Holmdel, Hazlet and Keansburg Sept. 15.
Monmouth County Commissioner Susan M. Kiley, liaison to the Department of Health and Human Services, told The Two River Times that after the June detection, the Office of Mosquito Control began treatments for mosquito larvae, “as well as its routine larval control and surveillance measures.”
“As mosquito species known to bite humans began testing positive for West Nile virus at an increasing rate, adult mosquito treatment was added as an additional measure to reduce mosquito populations and help protect public health,” she said.
WEST NILE VIRUS
According to the U.S. Centers for Disease Control and Prevention (CDC), “West Nile virus is the leading cause of disease spread by mosquitoes in the contiguous U.S.” While most infections are mild, according to the CDC, cases can be severe for some patients. Symptoms can range from fevers, headache, body aches, vomiting, diarrhea or rashes, and can potentially affect the central nervous system, resulting in hospitalization or death in extreme cases.
While no licensed vaccines or medicines currently exist to prevent or treat West Nile, the CDC recommends community-and household-level mosquito control. Using insect repellent registered with the Environmental Protection Agency, wearing long, loose-fitting shirts and pants to expose less skin, using screens on windows and doors, and avoiding outdoor activities during peak mosquito activity between dusk and dawn can also reduce risk. “The best way to protect yourself and your loved ones from West Nile is to prevent mosquito bites,” the CDC says.
West Nile virus activity typically peaks from mid-July through September, according to Kiley. Kiley seconded the CDC’s recommendations to use insect repellent and wear long-sleeve shirts and long pants when outdoors, and added that residents can also help prevent mosquitoes from breeding by “regularly emptying containers and other items on their property that collect standing water.”
PUBLIC HEALTH RISK
In Middletown, the first spraying took place Aug. 20 between 3 and 6 a.m., according to a county news release. The treatment area in Middletown included areas south of Route 36, east of 11th Street, Galloping Circle, streets east of Galloping Circle, areas south of Edgemoor Road, east of East Road and north of Sunrise Road.
In an Aug. 26 news release, the county announced a second round of spraying in Middletown for Thursday, Aug. 27, between 4 and 6 a.m. That treatment area covered both Port Monmouth and Belford, including residential streets east of Wilson Avenue, north of the Henry Hudson Trail and west of Ware Creek.
“Monmouth County is taking proactive measures to reduce the risk of mosquito-borne illnesses by continuously monitoring mosquito populations and using targeted treatments,” said Commissioner Director Thomas A. Arnone in the release.
A Monmouth County Mosquito Control Division Pesticide Fact Sheet made public by the county states that “while habitat management and measures to control immature mosquitoes in water are preferred and most used, the spraying of adult mosquitoes is called for when biting populations reach critical levels or when a disease organism is present in adult mosquitoes.”
While mosquito-borne illnesses do pose public risks, the insecticides used to combat them can pose health risks of their own. The Monmouth County Office of Mosquito Control uses DUET dual-action adulticide during its “control operations,” according to the county’s website.
DUET Dual-Action Adulticide’s Safety Data Sheet, effective Nov. 15, 2021, states that the chemical is “harmful if inhaled,” and “may be fatal if swallowed and enters airways.” The safety data sheet recommends avoiding “breathing mist/ vapors/spray. Use only outdoors or in well-ventilated areas.”
The safety sheet also states that the product has not been tested for reproductive or fertility impacts but is non-carcinogenic (cancer-causing).
DUET is a very fine mist sprayed into the air that must come into direct contact with the insects to be effective. Once sprayed, the county said “avoiding exposure is always the saf- est course of action,” according to the pesticide fact sheet.
The county advises residents to plan outdoor activities accordingly to limit time spent outside during treatment, and to bring pets, food and water bowls, clothing, and children’s toys inside during treatment times. Those in treated areas should avoid direct contact with surfaces wet with pesticides, which can take about an hour to dry after spraying.
Kiley assures that the mosquito treatment poses mini- mal risk to the public, “due to both the insecticide used, DUET, and the way it is applied. All staff applying insecticides for adult mosquitoes (also known as adulticides) are highly trained, NJDEP-licensed pesticide applicators.” Any insecticide the county uses, including DUET, is registered with the New Jersey Department of Environmental Protection and the United States Environmental Protection Agency, according to Kiley.
If one does come in contact with the pesticide, the fact sheet recommends flushing eyes and/or skin with water and monitoring for symptoms of over-exposure, which can include common symptoms such as irritation to skin and eyes, respiratory and nasal irritation, dizziness, headaches or nausea, but also “irritability to sound or touch, abnormal facial sensation, sensation of prickling, tingling or creeping of skin… excessive salivation, and fatigue.”
PROTECTING POLLINATORS
DUET remains airborne for a short time – anywhere from five to 30 minutes – but the active ingredients, pyrethroids and piperonyl butoxide, can remain in the soil for eight to 25 days.
The county uses the lowest amount of insecticide possible, “equivalent to approximately one-shot glass of active ingredient per football field of area, or approximately 1.3 acres,” Kiley said. In addition, the county uses what Kiley described as “ultra-low-volume technology,” or insecticide droplets that are incredibly small, designed to target mosquitoes while minimizing impacts on larger insects.
DUET is an adulticide, designed specifically to target adult mosquitoes. Applications are scheduled at night whenever possible, which not only reduces public exposure but is when “honeybees, native bees, and other day-active pollinators are not foraging,” Kiley said. “Applicators also maintain a proper distance from bodies of water when applying DUET and other adulticides because these products are toxic to aquatic organisms. DUET and other adulticides used by the county break down within hours when exposed to sunlight,” she said.
As of Aug. 28, “58 mosquito samples have tested positive for West Nile virus outside of Middletown Township and elsewhere in Monmouth County,” Kiley said. “Statewide, 537 mosquito samples have tested positive for West Nile virus.”
This article originally appeared in the September 17-23, 2026 print edition of The Two River Times.
