This summer, New Yorkers should be prepared to take measures to avoid the whining swarm of annoyances descending on the five boroughs -- and we're not talking about tourists. With a warm winter and a rainy spring, conditions are ripe for the annual onslaught of mosquitoes to be fiercer than usual.
Chanel Caraway, a spokeswoman for the New York City Department of Health and Mental Hygiene, said in an email that low levels of mosquito activity were detected throughout the city as of last week, but that recent higher temperatures and rain in the past few days may have promoted mosquito breeding in some parts of the city.
A lot of factors contribute to the emergence of adult mosquitoes: lots of warm days, lack of freezing temperatures, and the difference between precipitation levels and the amount of moisture evaporated. Cornell University's entomology department and the Northeast Regional Climate Center have an online tool that tracks all these factors, and it looks as though the time of the mosquito is nigh.
Since the start of the season, New York City's moisture surplus stands at somewhere between 2 and 3 inches, while as of Wednesday it's been around 90 days since the city felt a freezing temperature, according to the NRCC.
Adult mosquitoes will typically emerge after the accumulation of 230 of what are called base 50 daily degree days, according to preliminary research from Cornell and the NRCC. Degree days are calculated by adding the maximum and minimum temperatures for a day, dividing by two, and subtracting by the base (so for base 50, subtract 50). Any number greater than zero is the degree days for that day. Since March 15, New York City has accumulated between 600 and 675 base 50 degree days.
The NRCC also uses modeling tools to project the current adult and immature mosquito population at various points throughout the Northeast. In Central Park alone, the group estimates there are more than 8,000 immature mosquitoes and more than 1,000 adult mosquitoes as of Wednesday -- a figure within the 90th percentile of historically measured abundance.
Mosquito bites can sometimes be more than annoying -- they can also transfer diseases from the bug to the bitten. West Nile, which can lead to serious neurological diseases like encephalitis and meningitis, is perhaps the most famous of these. The disease is still fairly rare -- in New York state, there were just 44 cases and only 2 deaths in 2011, according to the U.S. Centers for Disease Control.
To avoid bites, the Department of Mental Health and Hygiene recommends people take precautionary measures like wearing long pants, avoiding shaded areas and using insect repellents.
But sometimes the city will bring out the big guns.
To kill mosquitoes, city health officials have two options: they can use a liquid insecticide to kill adults in residential or non-residential areas, or they can use helicopters to bombard marshes and other natural, non-residential areas with bacterial granules to kill mosquito larvae.
At the moment, officials have not scheduled any spraying activities, but they are applying larvicide to water bodies that are producing mosquitoes, department spokeswoman Caraway said.