NEWS FROM THE DELAWARE DEPARTMENT OF NATURAL RESOURCES AND ENVIRONMENTAL CONTROL
March 24, 2008
Vol. 38, No. 109
For more information, contact William Meredith, Mosquito Control, 302-739-9917, or Joanna Wilson, Public Affairs, 302-739-9902.
2008 Mosquito Control Season Begins with Spraying Wooded Wetlands This Week
Weather permitting, DNREC’s Mosquito Control Section will start its annual spring woodland-pool spraying on Tuesday, March 25, treating wooded wetlands near populated areas in New Castle, Kent and Sussex counties. A maximum of about 10,000 acres will be treated by helicopter, with the focus on areas near cities, towns and large developments.
Control efforts will target the immature (larval) stages of early-season woodland pool mosquitoes. Aerial spraying of woodland pools must be completed before the forest canopy leaf-out that usually happens around mid-April, because leaves will prevent the insecticide from reaching pools and other wet spots containing larvae on the forest floor.
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.
With about 100,000 acres of wet woodlands in Delaware, it is not possible for budgetary, logistical and environmental reasons to larvicide all mosquito-rearing habitats. “For best return-on-investment for providing mosquito relief to the most people, only woodland pools near populated areas will be treated,” said Mosquito Control Program Administrator William Meredith.
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, can be applied without posing unreasonable risk to human health, aquatic organisms, wildlife or the environment, Meredith said.
The amount of spraying needed is determined by how wet woodlands are, which can vary from year-to-year depending on the amount of precipitation over the past autumn and winter into early spring. Precipitation amounts and patterns over a period of several months affect shallow groundwater levels, which in turn determine whether woodland floor depressions or swales fill with and retain rainfall water. This year, woodlands flooding has been a bit below normal in many downstate areas, whereas in most upstate areas woodland flooding appears about normal. Overall for this spring, the state’s total wet woodlands acreage typically targeted each year for spraying is somewhat less than normal. However, rainfall amounts and patterns over just a few days could quickly change that, Meredith said.
The annual spring woodland-pool treatment program marks the beginning of Delaware’s mosquito control season, which in most years continues until around late October and can last as long as mid-November, depending upon when the first killing freeze occurs.
While some species of spring mosquitoes may carry West Nile virus, the mosquito species primarily responsible for transmitting this disease to humans - mainly the common house mosquito and its close relatives, and possibly the Asian tiger mosquito - arrive later in the year from sources other than woodland pools. The other mosquito-borne disease of concern to humans and horses, eastern equine encephalitis, is primarily transmitted by salt marsh mosquitoes during late summer and early fall.
Throughout the warm weather months, the Mosquito Control Section will be busy treating larval or adult mosquitoes originating from salt marshes, coastal impoundments, floodplain bottomlands, freshwater wetlands, grassy swales, wet meadows, wooded swamps, roadside ditches, stormwater management ponds and sewer catch basins, as well as container sources holding standing water for four or more days.
The public is encouraged to do their 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, and depressions in tarps covering boats or other objects stored outside.
For more information on Delaware’s Mosquito Control program, call 302-739-9917 in Dover. To request local relief, call Mosquito Control’s field offices, 302-836-2555 for New Castle and northwestern Kent counties, or 302-422-1512 for the rest of Kent and all of Sussex counties.
Advance public notice of when and where spraying will occur is given daily via radio announcements, on a toll-free hotline at 800-338-8181 or on DNREC’s website, www.dnrec.state.de.us/dnrec2000/Applications/Mosquito/index.asp. Interested parties may also subscribe to receive e-mail announcements by visiting the DNREC homepage, click on “Email List Subscription” under Services and follow directions to sign up for mosquito control spray announcements.
For more information on Delaware Mosquito Control, please visit http://www.fw.delaware.gov/Services/Pages/MosquitoSection.aspx.
