Mosquito Control Program Uses Airplane and New Larvicides to Kill Mosquitoes Where they Breed

ANNAPOLIS, MD –  This season, the Maryland Department of Agriculture (MDA) Mosquito Control program will use an airplane and two different insecticides to target mosquito larvae in wetlands and salt marshes to kill mosquitoes before they grow up and fly into populated area. This will not only reduce the need to spray for adult mosquitoes by thousands of acres later in the year, it will also reduce the risk of transmitting mosquito-borne diseases to people, dogs and horses.

“Using our aircraft and targeting larvae rather than adult mosquitoes reduces the number of acres we have to spray for adult mosquitoes later in the season, but more importantly, it reduces the risk of mosquito-borne diseases to people and pets,” said MDA Mosquito Control Assistant Chief David Schofield, who is based in Salisbury.

Larvae are concentrated in wetlands. Once the adults take flight, they can spread for miles, greatly increasing the area where they must be controlled. Controlling mosquitoes before they grow up reduces nuisance for local residents as well as the risk of mosquito-borne diseases.

Earlier this month, MDA’s Mosquito Control staff applied a bacterial larvicide during a two day period in a twin-engine Beechcraft, flying over and treating 4,208 acres of flooded woodland in Dorchester, Somerset and Worcester counties the Eastern Shore. The larvicide, called Vectobac 12AS (BTI), is a formulation of a naturally occurring bacteria which MDA has used for some time. This application killed 95 percent of the mosquito larvae in the targeted area. (A larva is the life stage of a mosquito between an egg and an adult.) A success rate of 95 percent across the entire treatment area was greater than expected because of weather and other conditions at the time of spraying and past performance.

This application targeted a species of mosquito (Ochlerotatus canadensis) that hatches early in the spring and lives in wooded, shaded areas. It is an aggressive biter and a particularly long-lived mosquito that feeds on mammals, birds and reptiles, especially turtles. It also helps transmits California group viruses, dog heart worm, West Nile virus and eastern equine encephalitis.   

Later in the season, as tides flood the high marsh areas and weather conditions are appropriate, MDA will spray by aircraft a new larvicide – called Natular 2E – against the larvae of the Eastern Salt Marsh mosquito (Ochlerotatus sollicitans) in the Fishing Bay and Elliot Island area of Dorchester County. The Eastern Salt Marsh mosquito is the primary pest mosquito of the Eastern Shore, is another aggressive biter of mammals and birds, and also transmits West Nile virus, eastern equine encephalitis and other diseases. This application is expected to reduce mosquitoes in the Elliot Island area as well as reduce the need for follow up spraying to control adult mosquitoes.

The two larvicides used are highly host specific and have minimal or no impacts on non-target species. They are also less toxic than the sprays used to control adult mosquitoes and can be applied over much smaller areas. Using a plane makes treatment of large areas of wetlands more economical and effective. Every acre that is successfully larvicided by plane may reduce adult spraying by thousands of acres.

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