By TIM FAULKNER/ecoRI News staff
For the first time since the early 1990s, pesticides have been sprayed to combat mosquitoes in Rhode Island. An independent pest company applied the insecticide sumithrin on the night of Aug. 23 to marsh areas in the Common Fence Point and Island Park neighborhoods in Portsmouth.
This needed extermination may or not be another sign of climate change, but warmer weather is to blame, according to Alan Gettman, mosquito abatement coordinator for the state Department of Environmental Management (DEM). “It was such an unusually warm winter that the (mosquito) population built quicker," he said.
Last December was the second warmest in Rhode Island since 1895. March was that state’s warmest ever, a full 7.7 degrees above the average, and the past decade has been the warmest on record. According to the Rhode Island Ocean Special Area Management Plan, winters are expected to be 5 to 7 degrees warmer by 2100.
Gettman said there is no direct link between last winter and climate change, but mosquitoes and other insects were predictably ubiquitous this year.
Fortunately, the mosquitoes in Portsmouth were just a nuisance to residents, and not the species carrying West Nile virus and Eastern Equine Encephalitis (EEE). Both diseases can be fatal. EEE has a one-third mortality rate and survivors pose a high risk of neurologic damage. West Nile virus is more common, but only about 20 percent of people infected show symptoms, often a mild fever. Less than 1 percent of cases are fatal.
This year, three mosquito pools in Rhode Island have tested positive for EEE and West Nile virus. Most recently, a positive report of EEE occurred Aug. 20 in north Tiverton. The Highlands J virus, which only infects birds, was detected near Wickford on Aug. 27.
Nearby southeastern Massachusetts is a haven for West Nile virus and EEE. The region's prevalence of hardwood freshwater swamps is ideal for infected mosquitoes, according to Gettman. Last year, a Raynham, Mass., resident died from EEE. This year, the illness is showing up in less common regions. A Worcester-area man died last week from EEE, an infection was reported in western Massachusetts and two cases were reported in Vermont, one fatal.
Gettman said both diseases can likely be found across Rhode Island. There are currently no plans for spraying to combat the diseases.
Cooler weather is the best defense against infected mosquitoes. By mid–September, they begin dying off and most are typically killed off with first hard frost in October. But not all die off, a small number of eggs, larvae and even mosquitoes make it through the winter.
“We can look forward to decreased mosquito biting as the weather becomes cooler in the weeks ahead,” Gettman said.
Until then, the DEM recommends eliminating mosquito breeding grounds from yards by removing standing water from old tires and buckets, to clean gutters so that they drain correctly, and maintain swimming pools properly. Wear protective clothing at dawn and dusk, and putting mosquito netting over playpens and baby carriages when they are outside.
Sumithrin (d-phenothrin) is a common pesticide against adult mosquitoes and other insects such as fleas, tics and bed bugs. It’s used for household, commercial and aerial spraying. According to the Environmental Protection Agency (EPA), sumithrin poses some chronic risks to mammals, and acute risks to honey bees and marine life. It is a suspected endocrine disruptor, a neurotoxin, and can cause kidney and liver damage.