Delaware aims to take bite out of mosquitoes

DNREC’s Mosquito Control Section dropped larvicide to treat 7,200 acres before forest canopy leafout arrived this spring.
(Submitted photo/DNREC)

DOVER — Throughout Delaware, the ground is as wet as it’s ever been.

Rain upon the First State with regularity last May, and this March was a soaker too.

Delaware’s Mosquito Control Section doesn’t know what comes next. Broods of the pests may have hatched so much in 2018 that there’s little left this year.

“We’re hoping that last year may have depleted the egg burden,” Program Administrator William Meredith said last week.

“At this point we’re in wait and see mode to learn the upcoming conditions.”

Mosquitoes begin to hatch in April, so the state’s experts got in front by using a helicopter to drop larvicide over 7,200 acres before forest canopies leafed out. Upcoming targets for the survivors include within city and town borders, subdivisions and other habitats with characteristics of early season pests.

The so-called “people biters” don’t transport “but are very concerning for quality of life and economic impact,” Mr. Meredith said.

He said residents begin calling with complaints in late April.

Despite the state’s best efforts, many eggs survive. Fog trucks filled with adulticide the road in late April for “hot areas.” Fixed wing aircraft add to the arsenal with applications.

There’s a statewide network of 26 permanent traps that collect mosquitoes to evaluate density. Mobile light traps collect them each day as well. Some staff members draw the duty of standing in areas, counting their bites and figuring out the density present to determine an attack plan.

Homeowners can help themselves by lessening or eliminating standing/stagnant water. If the mosquitoes breed in large wetland habitats, the Milford-based Mosquito Control section should be contacted at 422-1512.

According to Mosquito Control, “All of our insecticides are registered and approved by the U.S. Environmental Protection Agency and have been determined to pose no unreasonable risks to human health, wildlife or the environment.”

If possible, Mosquito Control Section uses non-insecticide control methods for source reduction in per-emergence larval stages, including:

• Water sanitation and elimination of container breeding habitats.

• Open Marsh Water Management, management of tidal flows and marsh water levels, and stocking of mosquito fish.

The Mosquito Control Section — part of the Department of Natural Resources and Environmental Control – has 18 full-time employees and about 15 seasonal employees as summer concerns mount.

Mosquito control FAQ

Frequently asked questions from Delaware’s Mosquito Control Section:

Question: Why are the mosquitoes bad around my house? What can I do about them?

Answer: Many adult mosquitoes around the home come from mosquito production sites within or near the neighborhood. To help reduce the number of mosquitoes, homeowners should eliminate or reduce standing/stagnant water on their property, especially containers like buckets, wheelbarrows, kiddie pools, bird baths, corrugated pipes, clogged rain gutters, and flower pot saucers. For larger mosquito breeding habitats like wetlands, roadside ditches, or stormwater management basins, contact the Mosquito Control Section office for your area. (See our contact information on the About Us page.) Click here for more information. Click here to view the Mosquito Control & Your Backyard video.

Q: Why do we need Mosquito Control?

A: The Delaware Mosquito Control Section’s mission is to control the state’s nuisance and potentially disease-bearing mosquito populations for the purposes of protecting public health, quality of life and economic interests.

Q: What kinds of insecticides are used and when?

A: The Mosquito Control Section utilizes insecticides as an important component of its Integrated Pest Management (IPM) program. Our IPM program involves the combination of various different control methods, including insecticides. All of our insecticides are registered and approved by the U.S. Environmental Protection Agency and have been determined to pose no unreasonable risks to human health, wildlife, or the environment. The two basic types of mosquito control insecticides are larvicides (for larval or the immature aquatic life stage of the mosquito) and adulticides (for control of adult mosquitoes). We currently use the following larvicides: BTI, methoprene, Spinosad, and monomolecular film. Our fog trucks apply sumithrin (a synthetic pyrethroid), and our aircraft applications use naled (an organophosphate).

Q: Why do you have to use insecticides? What other methods are used?

A: The Mosquito Control Section prefers, whenever practicable, to use non-insecticide control methods. There are several methods of source reduction through which mosquito-producing habitats are eliminated or mosquitoes are controlled in their pre-emergence larval stages. These methods include water sanitation and elmination of container breeding habitats, Open Marsh Water Management, management of tidal flows and marsh water levels, and stocking of mosquito fish. When source reduction is not possible, or practicable, insecticides are used.

Q: Are mosquito control insecticides safe? Should I be concerned if I’m exposed to spraying?

A: The Mosquito Control Section only uses insecticides that are registered by the U.S. Environmental Protection Agency for mosquito control purposes. The EPA has determined through its testing and review process that when these insecticides are applied according to the label instructions, their application “poses no unreasonable risks to human health, wildlife, or the environment.” For the general public, exposure to spraying will not cause any harm. Individuals that are hyper- or chemo-sensitive may experience mild allergic reactions and should consult a medical professional.

Q: How can I find out when and where mosquito control spraying might be done?

A: There are several different ways to find out when and where mosquito control spraying will be done. The most common way is through our email list server. You can subscribe to the email spray announcements through the Spray Zone Notification System at

Spray announcements are also made on our toll-free hotline at 1-800-338-8181 and are submitted to local radio stations (that may or may not air the announcements).

Q: What steps can I take to avoid exposure to mosquito control spraying?

A: To avoid exposure to mosquito control spraying, an individual can temporarily leave an area about to be sprayed or remain indoors with the windows and doors closed and the air conditioner(s) turned off during and immediately following an insecticide application.

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