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Skip Navigation LinksDNREC : News : DNREC Mosquito Control Sections spraying season begins with larviciding wooded wetlands

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Contact: Joanna Wilson, DNREC Public Affairs, 302-739-9902

DNREC Mosquito Control Section’s spraying season
begins with larviciding wooded wetlands

DOVER (March 17, 2016) – Weather-permitting, DNREC’s Mosquito Control Section will begin its annual spring woodland-pool spraying campaign downstate Saturday, March 19 and upstate Tuesday, March 22, treating wooded wetlands near select populated areas in New Castle, Kent and Sussex counties. About 10,000 forested acres that produce large numbers of early season mosquitoes will be strategically sprayed, using larvicides applied by helicopter and possibly fixed-wing aircraft.

A milder than usual winter with warmer temperatures has somewhat accelerated development of mosquito larvae in woodland pools,” said Delaware Mosquito Control Administrator Dr. William Meredith of DNREC’s Division of Fish & Wildlife. “With woodland flooding conditions a bit above normal upstate and a bit below normal downstate, the statewide average for woodland pool conditions is pretty typical so far – with potential for lots of mosquitoes to emerge.”

Aerial spraying of woodland pools must be completed before the forest canopy fills in, usually around mid-April, because leaves prevent the insecticide from reaching pools and other wet spots on the forest floor containing mosquito larvae. The spring campaign marks the beginning of Delaware’s annual mosquito season, which in most years continues until mid-October or early November, depending upon when the first killing frost occurs.

If larval stages of early season mosquitoes are not successfully controlled, an intolerable number of biting adult mosquitoes would take wing in late April and remain through late June, becoming particularly troublesome within one to two miles of their woodland pool origins, and significantly affecting quality of life and human health for residents and visitors alike, said Dr. Meredith 

“Delaware has about 100,000 acres of wet woodlands during most springs, and its not possible for logistical or budgetary reasons to larvicide all woodland mosquito-producing habitats,” Dr. Meredith continued. “Targeting the pools near populated areas is the best return on investment in providing mosquito relief to the most people.”

Over the next few weeks, Mosquito Control will apply a bacterially-produced insecticide, Bti. “Like all insecticides used by Delaware Mosquito Control, the U.S. Environmental Protection Agency has determined that Bti, when used in accordance with EPA-approved instructions as required by federal law, can be applied without posing unreasonable risk to human health, wildlife or the environment,” said Dr. Meredith.

The amount of spraying needed is determined by where and how wet the woodlands are, and can vary from year to year depending on the location and amount of precipitation that has occurred over the past autumn, winter and early spring.

With the Zika virus in the news recently, Dr. Meredith added that Mosquito Control’s annual spray campaign for early season woodland pool mosquitoes is not as focused on disease control – as the Section’s work will be later in the season. “Although public health officials and mosquito control professionals recognize that possible medical complications beyond itching can result from too many bites, spring woodland pool mosquitoes are not the primary disease carriers of concern in Delaware,” he said.

“The mosquito species in Delaware which could possibly transmit Zika is the Asian tiger mosquito, which won’t become a pest or health problem until sometime in May,” Dr. Meredith continued. “However, now is not too early for the public to take action to reduce backyard mosquito-producing habitat for species such as the Asian tiger mosquito that will occur later in the season and that are known to carry illnesses such as West Nile virus and chikungunya as well as possibly Zika.”

With disease concerns higher than normal heading into mosquito season, residents are strongly encouraged to reduce mosquito-producing habitat by cleaning clogged rain gutters and downspout extenders, keeping fresh water in birdbaths, draining abandoned swimming pools and preventing or emptying standing water from containers such as scrap tires, cans, buckets, flower pot liners, unused water cisterns, children’s toys, upright wheelbarrows, uncovered trash cans, depressions in tarps covering boats or other objects stored outside.

As in the past, advance public notice of when and where spraying for adult mosquitoes will occur this year will be available via daily radio announcements and by calling 800-338-8181 toll-free. Interested parties may also subscribe to receive email, text or phone message notices of mosquito control spraying in their area by signing up on the new Spray Zone Notification System at

To request localized mosquito control, call Mosquito Control’s field offices:

·       Glasgow Office, 302-836-2555, serving New Castle County and the northern half of Kent County, including Dover.

·       Milford Office, 302-422-1512, serving the southern half of Kent County south of Dover and all of Sussex County.

For more information about Delaware’s Mosquito Control program, call the Dover office at 302-739-9917.

DNREC’s Mosquito Control Section provides statewide services to about 935,000 Delaware residents and 7.5 million visitors annually to maintain quality of life and protect public health by reducing the possibility of mosquito-borne illnesses such as West Nile virus, eastern equine encephalitis, chikungunya and Zika virus. Throughout the warmer months, Mosquito Control monitors and treats mosquito populations that emerge from wetland areas found throughout the state, including ditches, stormwater ponds, wet woodlands and coastal salt marshes. The Section also works year-round on water and marsh management projects designed to reduce mosquito populations, and provides the public with information on dealing with mosquitoes, from reducing backyard mosquito production to avoiding mosquito bites.

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Vol. 46, No. 82
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