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Skip Navigation LinksDNREC : News : Aerial mosquito spraying conducted in Wilmington’s Cherry Island area

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Contact: Joanna Wilson, DNREC Public Affairs, 302-739-9902

Aerial mosquito spraying conducted in Wilmington’s Cherry Island area; Mosquito Control continues monitoring mosquito populations

WILMINGTON (Aug. 14, 2012) – On July 27, the DNREC Mosquito Control Section investigated and confirmed reports that a large mosquito brood was hatching out of a 100-acre dredge spoil site at the Cherry Island landfill site east of the City of Wilmington. In an attempt to control as many mosquitoes as possible while still in their immature aquatic larval stage, Mosquito Control began immediate aerial pesticide applications to the site.

Follow-up inspections revealed that many of the larval mosquitoes were unaffected by the pesticide, primarily due to the amount of water and sediment diluting the pesticide in the midst of the ongoing dredging activities. In addition, some were beginning to emerge as adult flying mosquitoes. Mosquito Control moved into monitoring mode to gauge the number and species of emerging adult mosquitoes.

Two surveillance traps set at Cherry Island on the evening of Aug. 1 captured 1,705 and 318 mosquitoes, respectively. Landing counts – the number of mosquitoes landing and attempting to bite a human in the course of one minute – yielded five per minute. Three additional traps were set on Aug. 2 in the Southbridge and East 7th Street areas to determine if the mosquitoes had moved into these more populated areas. One of the traps on the east side of Southbridge captured 345 mosquitoes. All the trapped specimens were counted and identified.

Due to the number of mosquitoes and the potential threat of West Nile virus (WNV), Mosquito Control recommended aerial pesticide application to City of Wilmington officials and received immediate approval.

“Conducting aerial spray operations in urban areas is rare, but in this case, we felt it is necessary to ensure the comfort of the community and reduce the chances of disease transmission,” said Tom Moran, Mosquito Control program manager for northern Delaware. “This time of year is typically when we begin to see the most West Nile activity, and the Cherry Island sentinel chickens have a documented history of West Nile findings. We’ve already found WNV in wild birds in northern New Castle County and in one sentinel chicken in the Stanton area.”

On the evening of Aug. 7, Mosquito Control sprayed to control adult mosquitoes at the entire Cherry Island landfill complex, the terminal end of the East 7th Street peninsula and the lands east of Christiana Avenue just east of Southbridge. Post-spray trap surveillance conducted the following evening showed a 91 percent reduction in the adult mosquito population at Cherry Island and a 73 percent reduction in the Southbridge area. No further adult control actions are planned at this time.

“With dredging activity at Cherry Island scheduled to continue for several weeks, Mosquito Control will continue to monitor the area and take action as needed,” Moran said. “Due to many of the species present being ‘after dark’ biters, ground fogging for adult mosquitoes may be needed in the Southbridge area.”

Since some of the species found in the Southbridge area traps are known to breed in artificial containers, residents can also take action to reduce the mosquito population, Moran noted. To reduce mosquito-breeding habitat, residents should drain or remove items in their yards that collect water, such as buckets, discarded cans, stagnant birdbaths, unprotected rain barrels, old tires, uncovered trash cans, upright wheelbarrows, flower pot liners, depressions in tarps covering boats, clogged rain gutters, downspout extenders, and unused swimming pools.

To help Mosquito Control determine when and where services are needed, residents statewide are encouraged to report intolerable numbers of biting mosquitoes or other concerns by calling the Section’s field offices: 

·         Glasgow Office (upstate) – at 302-836-2555, for all of New Castle County and the northern half of Kent County.          

·         Milford Office (downstate) – at 302-422-1512, for the southern half of Kent County south of Dover, and for all of Sussex County. 

Calls will be answered by staff from Monday through Friday between 8 am and 4 pm. Callers after business hours or during weekends or holidays should leave a message giving their name, phone number, address and a brief description of their need or problem.  

For more information, contact the Mosquito Control Section’s Dover Office at 302-739-9917 or visit

For more information about West Nile virus in humans, contact the Delaware Division of Public Health at 888-295-5156.

For more information about West Nile virus in horses, contact the Delaware Department of Agriculture at 302-698-4500 or 800-282-8685 (Delaware only).

Vol. 42, No. 313

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