The following is a graph of the daily high tides predicted to occur at the Neponset River outflow in Boston/Quincy, Massachusetts. The graph is relatively close to the predicted tides elsewhere in eastern Massachusetts, including the Norfolk County Mosquito Control towns of Braintree, Milton, and Weymouth. The graph is important for mosquito control personnel because the salt marsh mosquito’s life cycle is in synch with the monthly tidal cycle, as well as rainfall. Since the tides are predictable, the emergence of this mosquito is also predictable. Unusually large rain events can also trigger salt marsh mosquito emergences. These occurrences are, of course, unpredictable.

Summer 2024

For residents who live near salt marshes that breed this mosquito, one can use this graph to predict when larger than usual outbreaks will most likely occur. The dates on the chart represent the date of the spring high tide (“spring” referring to the highest tide of the month, not the season). Simply add 7-10 days to this date and the mosquito outbreak is predicted. This summer, the likely dates of the more severe mosquito outbreaks in Massachusetts coastal towns start around May 15th, June 12th,  July 3rd, July 30th, August 28th, September 27th and October 25th.  Salt marsh mosquitoes are some of the most aggressive biting mosquitoes in our region. In light of this, The District engages in an active larvicide program of known breeding sites on the salt marshes and visits these sites after these spring high tides to reduce the nuisance from these aggressive salt marsh mosquitoes. This reduces the need for truck spraying in these areas.