Delaware Division of Fish & Wildlife

Hello, this is Bill Meredith, Program Administrator of the Delaware Mosquito Control Section. Welcome to the Mosquito Control website, and I thank you for the opportunity to provide an overview of our program. Please let me focus below on the "what, why and how" for our operations, and conclude with information for contacting us about any questions or problems.

Delaware mosquitoes. Delaware’s expansive coastal marshes, extensive swampland forests, scattered wet woodlots, and flooded swales can all produce massive swarms of mosquitoes if not controlled. Mosquitoes have always been troublesome in Delaware, but as more people over the past few decades have moved closer to mosquito-breeding habitats, problems have substantially increased. Without control efforts, mosquitoes can be as abundant in well-established urban and suburban areas as in newly-settled exurban or rural locations, breeding almost anywhere permanent or temporary standing water is found.

Given flight ranges of mosquitoes that vary by species from ¼-mile up to 15-20 miles, these insect pests can affect many Delaware residents and visitors, both urban and rural. Of the approximate 59 species of mosquitoes found in Delaware, 17 are of concern to humans or domestic animals because of their feeding preference, abundance, flight range, or potential as disease vectors. The Section has a statutory mandate to provide relief to Delawareans from problems that mosquitoes cause.

Problems that mosquitoes cause. There are 3 major problem areas – nuisance, disease, and economic impacts.

Nuisance -- Anyone who has spent much time outdoors in Delaware from April through November knows that one reason to control mosquitoes is for quality-of-life purposes, due to potentially intolerable nuisance or annoyance problems. Many people might expect close encounters with mosquitoes when recreating outdoors – e.g. campers, anglers, hikers, birders, boaters, canoers, or hunters – but even here there are tolerance limits for what takes wing. Other people being outdoors usually do not view mosquitoes as an acceptable part of their environs – e.g. joggers, backyard gardeners, Little League fans, dog walkers, guests at outdoor weddings, bikers, graduation ceremony attendees, boardwalk strollers, fireworks observers, picnickers, outlet shoppers, children on playgrounds, State Fair goers, beach sunbathers, park bench sitters, or people merely going down their driveway to check the mailbox or walking across a parking lot to their office. Landing rate counts of only one biting female mosquito per minute, experienced as your child plays for a half-hour after dinner in the backyard, can result in 30 very uncomfortable itches at bedtime. And then there are folks who have to make their living outdoors, where mosquitoes can make for a truly miserable workday – e.g. farmers, horse trainers, watermen, loggers, dairymen, construction workers, utility linemen, marina owners, heavy equipment operators, highway laborers, mail carriers, loading dock workers, or landscapers. You get the picture -- without mosquito control, a lot of outdoor Delaware would be rather unpleasant for much of the year, and in some areas border on unlivable or unworkable.

Disease -- Another very important reason to control mosquitoes is because of potential impacts on public health. Up through the early 20^th century, mosquito-borne diseases such as malaria or yellow fever occurred in Delaware, but modern mosquito control practices have almost eliminated these scourges from the southeastern United States. Today our primary concern in Delaware for mosquito-borne disease is viral encephalitis, either in the form of Eastern Equine Encephalitis (EEE) or caused by recently arrived West Nile Virus (WNV). In terms of clinical severity, human responses to contracting viral encephalitis vary widely among individuals. Mosquito-caused encephalitis can sometimes result in fatalities or long-term neurological damage, particularly for infants, children or the elderly, with EEE being more virulent than WNV. Both of these viral diseases can also affect horses and have high equine fatality rates. While there is an equine vaccine for EEE, none has yet been developed for WNV. We have concerns too about canine heartworm, a parasitic nematode affecting dogs, which fortunately is avoidable by preventive medication. There are also possible medical complications to humans even from "nuisance bites" free of virus, in that the child above who was bitten 30 times might excessively scratch or irritate the bites, often resulting in troublesome infections. Lastly, if mosquito infestations are severe and prolonged enough especially in residential areas, there can actually be mental health problems for some people.

Economic impacts -- Finally, uncontrolled mosquito populations can take a substantial toll on local economies based on tourism, outdoor recreation, or animal husbandry, and can even adversely affect property values. If given an option, not too many people will voluntarily choose to play, work or live where mosquitoes rule. The costs of not controlling mosquitoes far exceed what the State spends to limit their pestilence, with the Mosquito Control Section’s annual budget being about $1.5 million per year.

How does the Section respond? The Mosquito Control Section has 20 full-time employees and up to 17 seasonal employees to address statewide a potentially serious problem. Mosquito control work goes on year around in Delaware, focused on controlling larval and adult mosquito populations or on treating potential or actual mosquito-breeding habitats. The Section uses a modern Integrated Pest Management (IPM) approach having two primary components – source reduction and judicious use of insecticides.

Source reduction. Source reduction methods are non-insecticide means to eliminate or reduce mosquito larvae (immature mosquitoes in their aquatic life stage), and include stocking mosquito-eating fish in locations such as small freshwater ponds or stormwater management basins. But the more important source reduction methods involve water management practices such as:

• selective excavation of shallow ponds and ditches in wetlands to usurp mosquito egg- laying sites, and to increase predation on mosquito larvae by naturally resident mosquito-eating fish [a practice known as "Open Marsh Water Management" when done in unimpounded coastal marshes];

• manipulation of water levels in impounded coastal marshes to cause unfavorable conditions for mosquito egg-deposition or larval survival;

• removal or dumping of standing stagnant water associated with "container-breeding" freshwater habitats (e.g. discarded cans or drums, flower pot dishes, unused swimming pools or birdbaths, clogged rain gutters, used tires, etc.), particularly in urban or suburban areas.

Insecticide use. Unfortunately, in many areas and situations and for many reasons, source reduction methods are not always practicable or permissible to do. It is then necessary to use insecticides, which can be applied to control either larval or adult mosquitoes.

When insecticides are needed, our preference is to first use larvicides to treat immature mosquitoes in their wetland breeding habitats, which also limits insecticide exposure for people. Treating localized wetland areas where mosquito larvae thrive usually involves spraying much less area than having to treat uplands after adult mosquitoes have emerged and spread out. However, for various reasons such as poor weather conditions, timing and development stage of a mosquito brood, dense canopy or vegetation cover, or inaccessible breeding locations, it is not always possible to control larval populations by timely larvicide spraying. This can then result in occasional need for rapid-response adulticide spraying over more widespread and often populated areas.

All insecticide spraying is based upon pre-spray field surveillance that includes larval dipping counts, adult light trap collections, adult landing rate counts, and numbers and locations of public complaints.

The Section only uses larvicides or adulticides registered by the U.S. Environmental Protection Agency (EPA) for mosquito control purposes. The EPA has determined that these insecticides, when used in accordance with EPA-approved label instructions, can be applied to kill mosquitoes without posing unreasonable risks to human health, wildlife or the environment.

To the extent feasible the public is provided advance notice of our adulticide spray events through: 1) a toll-free number that can be called for a taped message; 2) by notices on the Internet at our Mosquito Control Section website; and 3) by public service announcements on local radio stations. When spraying is done in a municipality, local city or town officials might also give additional advance notice.

Where we now stand, and where we want to go. Many areas in Delaware formerly overrun by mosquitoes are now almost "mosquito-free," but this is only because of constant behind-the-scenes efforts by Mosquito Control personnel, whose good work often goes unappreciated by the public. Typically, we often seem to be recognized only when we fail to control a mosquito brood, with a relatively "pest-free" environment now apparently a modern right of life, with little thought by the public for how this has come about. It would not be the first time we heard folks who fail to make this connection rhetorically pose: "What do we need mosquito control for, the mosquitoes aren’t that bad!" Without continuous and diligent mosquito control efforts, a former era of problematic pestilence would quickly return. We will of course continue to provide our important public service, but we also want to increase the public’s knowledge about what we do and why and how we do it (with your kindly taking the time to read this webpage a most appreciated start).

However, we by no means have a 100% success story. There are still locations in Delaware where, because of nearby mosquito-breeding habitats that are difficult to treat or due to various other factors, and despite our best intentions and good efforts, the situation occasionally is anything but "mosquito-free." Wherever such problematic situations occur, particularly in or near populated areas, to the extent practicable we will continue to use source reduction and insecticides to provide whatever relief we can, with the outcome usually still much better than if there was no mosquito control at all. And for all areas in Delaware where mosquitoes can be problems, whether now fully "under control" or not, we will continue to examine and implement newer, better mosquito control methods as such improvements develop. In particular, we are always interested in new approaches that satisfactorily control mosquitoes in cost-effective manner while lessening any non-target impacts.

Wetlands habitat restoration/enhancement. As part of the Delaware Division of Fish and Wildlife, the Mosquito Control Section has much interest in restoring or enhancing wetlands habitats to benefit fish and wildlife populations. Because of the Section’s scientific and technical expertise, and because of our marsh equipment and mandated mission, we often have excellent opportunity to restore or enhance wetland habitats. In association with our Open Marsh Water Management (OMWM) work, or with our management of coastal marsh impoundments for tidal exchanges, water levels and microhabitats, local environmental conditions can often be improved for many wetland species.

Of special note is the Section’s lead role in DNREC’s Northern Delaware Wetlands Rehabilitation Program (NDWRP), an undertaking to restore up to 10,000 acres of degraded urban wetlands along the Christina/Lower Delaware River corridor.

How to contact the Mosquito Control Section. The Section has two operational facilities, one servicing upstate areas and the other for downstate locations, which are centers for both public contact and treatment response:

New Castle County (Bear Office), at 302-323-4492 (Tom Moran, F&W Regional Manager).

Kent/Sussex Counties (Milford Office), at 302-422-1512 (Dave Saveikis, Program Manager II).

If you have a mosquito nuisance complaint, or if you want to report finding suspect mosquito-breeding habitat, please call the number above for your respective county.

If you want to report a dead wild bird that might have died from West Nile Virus, you should call one of the two numbers above from 8:00 am-4:00 pm on weekdays. However, if you want to report a dead wild bird afterhours or on a weekend, please call

1-800-523-3336 (but kindly do not call this 1-800 number during the Section’s regular working hours). At present, the Section is only interested in reports about dead crows, blue jays, or hawks and owls.

If you want advance notice about our upcoming adulticide spray events (regardless whether we intend to spray by aircraft or truck), which because of many factors can only be announced from 4-24 hours in advance of spraying, please call 1-800-338-8181 for a taped message; or you can go to the Mosquito Control Spray Announcements on this website, at http://www.dnrec.state.de.us/fw/mosquito.htm

Finally, if you have a question or want information about any aspect of the Section’s policies, operations or practices, or about mosquito biology or wetlands ecology, you can call either the New Castle or Kent/Sussex Mosquito Control Offices at the two numbers listed above; or you can call me at the Mosquito Control Section Administration Office in Dover, at 302-739-3493. You can also contact me by e-mail, using the convenient "E-Mail Request!" box at the top of this webpage. If you wish to write me by U.S. Mail, please send your letter to: William H. Meredith, Delaware Mosquito Control Section, Division of Fish and Wildlife, DNREC, 89 Kings Highway, Dover, DE. 19901.

Thank you for visiting this webpage and our website. I hope you find the information useful.