Week 33 – Aug 10-16


Report based on data collected from traps deployed the week of August 10-16, 2014. Report prepared by Chan Suom, Dave Lawson, and Nate Boonisar.


CDC Light Traps:
CDC light trap collections continue with mostly lower than average numbers of mosquitoes from all of Norfolk County. Only the towns of Millis and Weymouth reported higher than usual activity levels of host-seeking mosquitoes.

Gravid Traps:
Even with a fresh brew of oviposition attractant solution, gravid trap activity continues to be lower than the historical average for most towns.


CDC Light Traps:
The most abundant mosquito species this week continue to be Coquillettidia perturbansof which over 600 specimens were collected from across the county. All other species remain low in abundance.

Gravid Traps:
Culex pipiens/restuans are the main species in these traps and their overall population is lower than average for this time of the season.


The overall mosquito population for host-seeking mosquitoes in CDC light traps is lower than average when compared with the historical average (2007-2013). Coquillettidia perturbans populations from our county-wide traps have dropped to a fifth of last week’s catch, from approximately 3,000 specimens to a little over 600. All other species remain relatively low in abundance.

Gravid trap collections have been lower than average thus far this season. A refreshed brew of mosquito oviposition attractant solution has not yielded an increase in trap counts of gravid mosquitoes.

Our experience lines up with those of other mosquito control districts in Massachusetts. Mosquito abundance levels have been low this season across all species and per trap type. So far we have only 2 WNV positive mosquito isolations as compared to 9 positive virus isolations from last season at this time of year. This week’s torrential rain event and the accompanying cool evenings have further reduced mosquito activity for the moment. This rainfall could potentially provide new habitat for more mosquitoes as it has been relatively dry for the last 90 days. Should this hold true, we will expect to see more mosquito activity within the next 10-14 days.

Please refer to our surveillance charts for detailed trap collection data.


Wednesday brought a widespread rainfall to the district on Wednesday. Heaviest amounts were in the west where up to 2 inches of rain fell in Bellingham.  Amounts trailed off to the east where around ¾” fell in Weymouth. More rain fell pre-dawn Friday when a thunderstorm moved from Wrentham to Holbrook with amounts of ¼ to ½ inch. Despite the rainfall, amounts over the past 30, 60, and 90 day periods remain between 50 and 75% of normal, with the driest conditions in the east.

Total weekly rainfall: 1.18 inches (+0.42 in.)
Total Monthly rainfall: 1.57 inches (-0.13 in.)
Total Yearly rainfall: 25.20 inches (-0.83 in.)


We received 331 calls for service this week. We have recorded a total of 7,221 service requests for the year.


The District continues to respond to requests for spraying with our evening ULV application program. Catch basin treatments are now completed for the season. The District has encouraged the towns where WNV isolations have bound found to encourage their residents to take personal precautions against mosquito bites, especially the elderly and immune compromised. A small number of larvicide requests from residents continue to be checked as needed. The District is currently conducting some ‘low-flow’ water management projects.


144 Production Rd, Suite C

Walpole, MA 02081

Office: (781) 762-3681
Fax: (781) 769-6436