Weather permitting, DNREC’s Mosquito Control Section will start its annual spring woodland-pool spraying Friday, March 26, treating wooded wetlands near populated areas in New Castle, Kent and Sussex counties.


Weather permitting, DNREC’s Mosquito Control Section will start its annual spring woodland-pool spraying Friday, March 26, treating wooded wetlands near populated areas in New Castle, Kent and Sussex counties. Approximately 7,000 to 10,000 acres with woodland pools where early season mosquitoes breed in quantity will be strategically larvicided by helicopter and possibly aircraft.

If larval stages of these early season mosquitoes are not successfully controlled, an intolerable number of biting adult mosquitoes could take wing by early to mid-May and remain through late June, becoming particularly troublesome within one to two miles of their woodland pool origins, and significantly affecting local quality of life for residents and visitors alike.

According to Mosquito Control Administrator Dr. William Meredith, only woodland pools near populated areas will be treated as in past years.

“Delaware has about 100,000 acres of wet woodlands and it is not possible logistically or for budgetary and environmental reasons to larvicide all woodland mosquito-rearing habitats,” Meredith said. “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 the Section, the U.S. Environmental Protection Agency has determined that Bti, when used in accordance with all EPA-approved instructions as required by federal law, can be applied without posing unreasonable risk to human health, wildlife or the environment,” Meredith said.

The amount of spraying needed is determined by where the woodlands are and how wet they are, which 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. “Woodland pool wetness in downstate areas is much higher than in recent years due to higher-than-average amounts of winter precipitation and recent rains,” Meredith said. “Spurred by these extremely wet conditions, we’ll probably see a lot of adult woodland pool mosquitoes in May and June, but less in or near the areas we sprayed.”

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

Effective with this spring spraying season, the coverage areas of Mosquito Control’s two field offices in Glasgow and Milford have been changed to better accommodate and service residents’ calls statewide. Glasgow Office staff will continue to cover New Castle County and northwestern Kent County while expanding into central Kent County north of a line extending from Kitts Hummock on Delaware Bay southwest to Magnolia, northwest to Camden-Wyoming, and then southwest along Route 10 to Sandtown, including these five towns. This new area also includes all of Dover, plus Hartly, Marydel, Bombay Hook National Wildlife Refuge and Little Creek and encompasses zip codes 19901, 19904, 19934 and 19962. Residents in these areas with mosquito control needs or concerns including intolerable infestations can call the Glasgow Office at 302-836-2555.

Milford Office staff will continue to cover Sussex County, with reduced responsibility in Kent County. Their jurisdiction south of the new Kent line includes Bowers Beach, Woodside, Viola, Frederica, Felton, Milford and Harrington. Their Sussex jurisdiction continues to cover Prime Hook National Wildlife Refuge, the Inland Bays, the coastal resort areas from Lewes to Fenwick Island, and inland population centers such as Georgetown, Seaford or Laurel.  Residents of southern Kent County and all of Sussex County with mosquito control needs or concerns including intolerable infestations can call the Milford Office at 302-422-1512.

As in the past, advance public notice of when and where spraying will occur this year will be given daily via radio announcements, by calling 800-338-8181 toll-free, or by visiitng http://www.fw.delaware.gov/services/MosquitoSection.htm . Interested parties may also subscribe to receive email notices by visiting the DNREC homepage — click on “Email List Subscription” under Services and follow directions to sign up for mosquito control spray announcements.

During mosquito season, the public is encouraged to do its part to reduce mosquito-rearing habitat by cleaning clogged rain gutters, keeping fresh water in birdbaths, draining abandoned swimming pools and emptying standing water from such containers as scrap tires, cans, flower pot liners, unused water cisterns, upright wheelbarrows, uncovered trash cans, depressions in tarps covering boats or other objects stored outside.   

For more information about Delaware’s Mosquito Control program, call 739-9917.