The Delaware Department of Natural Resources and Environmental Control’s Mosquito Control Section within the Division of Fish & Wildlife is scheduled to begin its annual spring woodland pool spraying March 19 to control immature aquatic mosquito larvae in wooded wetlands near select populated areas.

Weather permitting, spraying will begin in southern Sussex County and expand into Kent and New Castle counties in the weeks ahead.

Areas to be sprayed are determined by the location and size of woodland pools, which can vary from year to year based on precipitation levels from the past autumn, winter, and early spring. High precipitation levels have resulted in more extensive and above normal woodland pool habitat this year. It is not possible for logistical or budgetary reasons to spray 100,000 or more acres of Delaware’s woodland mosquito-producing habitats, so wet woodlands near the state’s most populated areas are targeted to provide the best return-on-investment in providing mosquito relief to the most people.

Over the next several weeks, Mosquito Control will apply the bacterially-derived insecticide Bti, which, as with all registered insecticides used by Delaware Mosquito Control, the U.S. Environmental Protection Agency has determined can be applied in accordance with EPA-approved product label instructions as required by federal law without posing unreasonable risks to human health, wildlife or the environment.

Aerial spraying of woodland pools must be completed before the forest canopy fills in, usually around mid-April, because foliage prevents the insecticide from reaching woodland pools and other wet spots on the forest floor harboring mosquito larvae. Control of larval stages of early-season woodland pool mosquitoes helps limit intolerable numbers of biting adult mosquitoes emerging in late April and lasting through mid-June that would affect quality of life and human health within 1 to 2 miles of their woodland pool origins.

The spring woodland spraying campaign for mosquito larvae marks the beginning of Delaware’s annual mosquito control season, which in most years continues until mid-October or early November, depending upon when the first killing freeze occurs. Control activities will be expanded starting in late April to adult and larval saltmarsh mosquitoes, other freshwater mosquitoes and urban and suburban container-breeding mosquitoes, to include control of adult woodland pool mosquitoes that still emerge.

Residents are encouraged to help reduce mosquito-producing sites by doing some outdoor “spring cleaning” by emptying or eliminating backyard artificial containers that hold water and produce mosquitoes later in the spring, such as the Asian tiger mosquito known to carry illnesses including West Nile virus. Backyard mosquito-producing standing water can be reduced 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 saucers, unused water cisterns, children’s toys, upright wheelbarrows, uncovered trash cans and depressions in tarps covering boats or other objects stored outside.

The public can learn about locations and times of spraying for mosquitoes via daily radio announcements or by calling 800-338-8181. Interested parties also may subscribe to receive email, text, or phone message spray announcements for their area by visiting

To request localized mosquito control, call Mosquito Control’s field offices in Glasgow, serving New Castle County and the northern half of Kent County, including Dover, at 836-2555; or in Milford, serving the southern half of Kent County south of Dover and all of Sussex County, at 422-1512.

For more, call 739-9917.