Tackling mosquito population growth at Delaware landfill

Delaware environmental workers are tackling a large population of stubborn mosquitoes living and breeding at a 100-acre dredge spoil site at Cherry Island landfill near Wilmington.

In late July, the state’s Mosquito Control Section identified the area around the landfill spoil site as home to a massive brood of mosquitoes.  An effort to kill as many as possible while they were still in their immature aquatic larval stage through aerial spraying didn’t work as expected due to the amount of water and sediment that diluted the pesticide.

Growing population

On August 1, two surveillance traps set up at Cherry Island collected more than 2,000 mosquitoes.  Landing counts, which track the number of mosquitoes landing and trying to bite a human over one minute, yielded an average of five bite attempts per minute.  

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At the Department of Natural Resources Request, the city of Wilmington approved aerial spraying of the area which happened on August 7.  A survey of the area after the application of pesticide showed a 91 percent reduction of adult mosquitoes at Cherry Island and a 73 percent reduction in the city’s Southbridge area.

“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.”

Be Vigilant

The state Division of Public Health is urging residents to “be vigilant in protecting themselves from mosquito bites.”  Public Health Director Dr. Karyl Rattay wants “medical providers to be familiar with West Nile symptoms and treatment.  When in doubt, test for the disease.”

Those symptoms include headache, high fever, stiff neck, and/or tremors and muscle weakness.  Only 20 percent of those infected with the the West Nile virus will become ill and develop symptoms.  Many cases likely go unreported.  The elderly and those with weakened immune systems are most at risk.

More spraying

A resurgence in mosquito numbers is not out of the question for the area south of Wilmington, especially with the ongoing dredging work.  “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.”  

He says residents in the area can help in the fight by reducing areas for mosquitoes to breed.  That includes draining items that collect water such as buckets, discarded cans, stagnant birdbaths, old tires, uncovered trash cans and unused swimming pools.  

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