When Will the EEE Threat End?

Mosquitoes are as synonymous with summer as sunburns, ice cream and heat waves. From their emergence in spring to their final days in autumn, you can encounter them anywhere from the cities to the suburbs. And with the recent rise in the number of cases of eastern equine encephalitis, they've become public enemy number one.

Spraying and bug juice (insect repellent with DEET) can only go so far in combating EEE, though. What do we need to wipe out the population? And when will it be safe to venture into the woods — without buttoning up and spraying down — again?

You know the answer is weather-related, or I wouldn't be writing this blog. Since mosquitoes are cold-blooded, any amount of cool air will quickly slow them down. A simple dip to the 50s can be enough to decrease their activity, but a wholesale freeze will put them in a permanent deep-sleep (or cause them to hibernate). Unfortunately, the first season frosts are a fickle thing, and it really depends on where you live.

Cool mornings in the suburbs are easier to come by in the fall than in the big cities. Thanks to the urban heat island (a whole other topic for another blog), the "concrete jungle" of the city landscape incubates the urban centers and makes them warmer than the suburbs. While our average date for the first frost in Boston and Worcester is Nov. 4 and Oct. 16, respectively, the average date in the suburbs is Oct. 7.

Before you bust out the champagne, remember that this is an average date, not a hard, fast promise for mosquito mortality. We've seen frosts in the suburbs as late as the Oct. 28 in 2011, and as late as Dec. 6 in 2009 in Boston! And with the current, mild (occasionally warm) pattern underway, there are no signs of frost in the immediate future.

Furthermore, while a frost may seriously diminish the mosquito population, a freeze is what's needed for a wipeout. Frosts are when the temperature dips near or below freezing for a short period of time. Freezes, on the other hand, are where the temperatures dip below freezing for several hours. For the suburbs, that means the wait may be as late as Oct. 12; in Worcester, the 21st; and for Boston, it's usually around the 11th of November.

As we play the waiting game, it's important that you follow the advice of local town administrators as well as the suggestions on the commonwealth's website. And while you're at it, get rid of any standing water outside. Pails, puddles, clogged gutters, wheelbarrows — they're all perfect breeding grounds for mosquitoes.

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