State's mosquito control tactics evolve

When Delaware’s first game warden took office in 1911, mosquito control consisted of a quick slap, preferably before an annoying bite. By the early 1930s, the first organized efforts by the newly formed Mosquito Control Commission consisted of draining Delaware’s myriad marshes in an attempt to reduce mosquito breeding.
As the Department of Natural Resources and Environmental Control's Division of Fish and Wildlife celebrates the first 100 years of fish and wildlife conservation by reflecting on the past and moving into the future, here’s a closer look at how the Commission evolved into the present Delaware Mosquito Control Section, which uses modern insecticide science and water management to control mosquito breeding and reduce adult mosquito populations, so that Delawareans don’t have to rely on that quick slap alone.
“Since its beginning nearly 80 years ago, Delaware Mosquito Control has provided our citizens and visitors with an invaluable service. Their methods have changed as the science has progressed, but Mosquito Control’s mission to improve our quality of life by reducing mosquito populations throughout the state continues today,” said DNREC Secretary Collin O’Mara.
The story of Delaware mosquito control begins in the midst of the Great Depression, when the federal government was putting men back to work through projects like the Civilian Conservation Corps (CCC). In 1933, under the direction of the Mosquito Control Commission, the CCC brought crews to the First State to brave winter cold, spring rains and summer heat - and mosquito bites - to dig extensive “parallel-grid” ditches for saltmarsh mosquito control.
“While parallel-grid-ditching helped reduce mosquito production in some areas, it also had some undesirable impacts on fish and wildlife habitat in our coastal wetlands, mainly by excessively draining larger natural ponds within the marsh,” said Dr. William Meredith, Delaware Mosquito Control administrator.
From the mid-1940s to the early 1960s, along with maintaining the parallel-grid ditch network, state mosquito control practiced ground and aerial spraying of insecticides as their primary control approaches. Early insecticides were relatively broad-impact products sometimes having long-lasting negative environmental effects, Meredith said. In the early 1960s, the first insecticides for adult mosquito control (adulticides) having short-lived environmental presence were adopted for use. Research and adoption of short-lived insecticides targeting mosquito larvae (larvacides) began in the mid-1960s and continues today.
In 1945, the powers, duties and functions of the Mosquito Control Commission were transferred to the State Highway Department. In the late 1950s and early 1960s, Mosquito Control collaborated with the Delaware Board of Game and Fish Commissioners (predecessor to the Division of Fish and Wildlife) to construct high-level coastal impoundments in the Port Mahon-Little Creek area east of Dover and in Sussex County’s Little Assawoman Bay, for the dual purpose of improving waterfowl habitat and supporting saltmarsh mosquito control.
In 1971, Mosquito Control moved from the State Highway Department to the newly-established Department of Natural Resources and Environmental Control. The following year, Mosquito Control became part of the Division of Fish & Wildlife, where the section continues to work today to control mosquitoes in concert with the division’s other goals of fish and wildlife conservation and wetland habitat creation, restoration or enhancement projects, Meredith said.
In 1979, Mosquito Control took a new, more natural approach to saltmarsh mosquito control with its Open Marsh Water Management (OMWM) program. Instead of using the old parallel-grid ditching method, Mosquito Control creates or restores small ponds and spur ditches as environmentally compatible open water areas in salt marshes to discourage mosquito larvae production, increase the role of native fish in consuming mosquito larvae and provide habitat for waterfowl and other wildlife. OMWM systems have now been installed in several thousand acres of Delaware’s coastal wetlands. In the early 1980s, the section also added a fish-stocking program using small native fish to help control freshwater mosquitoes in select habitats.   
In their 1986 report the Wildlife Management Institute notes the logic behind the section’s transfer to the Division of Fish and Wildlife. “Mosquito Control affects wetlands management more than any single activity,” the report states, then sums up one of the section’s continuing missions, “The work in open marsh management uses a biological approach to mosquito control that reduces the pest insects without loss of fish and wildlife habitat.”
Today, in addition to water management and biological control methods, Delaware Mosquito Control uses trucks, helicopters and aircraft equipped with sprayers and state-of-the-art GPS and GIS technologies to accurately apply larvicides to woodland pools in early spring and to salt marshes from late spring through autumn, along with using adulticides as needed during the warmer months of high mosquito production.
To help plan and focus their control efforts, Mosquito Control encourages the public to call to report intolerable numbers of biting mosquitoes in their areas. In Sussex and southern Kent counties, call the Milford Office at 302-422-1512. For more information about Mosquito Control, call the Dover office at 302-739-9917.
Mosquito Control also maintains monitoring stations for two mosquito-borne illnesses that affect humans and horses, West Nile virus and Eastern Equine Encephalitis (EEE), and also monitors wild birds for West Nile. From 2000 to the present, the University of Delaware has assisted Mosquito Control with West Nile virus field research. Previously, from the mid-1930s to the late 1970s, the University had assisted Mosquito Control with planning and assessments of mosquito control efforts, along with research in mosquito biology and ecology.
“As fish and wildlife conservation enters its second century in Delaware, the Mosquito Control Section has evolved from ditch-digging to cutting edge science. Today, the Section plays a vital role in contributing to the public health and quality of life for our citizens as well as helping the Division of Fish and Wildlife achieve its mission to protect, restore and conserve wildlife habitat and populations for the future,” said division Director David Saveikis.