Week 40 – Sept 30-Oct 1

2008 Mosquito Report: Week 40

Report based on data collected from traps deployed on Tuesday, September 30, 2008 and retrieved on Wednesday, October 1, 2008. Report prepared by John Smith, Chan Suom, M.S., and Nate Boonisar.

1. Current mosquito activity/trend

CDC Light Traps:
CDC mosquito activity in general has dropped and remained low across the county. Some towns have expressed higher mosquito counts. This is a result of recent rain events and represents flood hatch species such as Aedes vexans and Ochlerotatus trivittatus as evidenced in traps deployed in Bellingham,Canton, Dedham, Franklin, Millis, Norfolk, and Walpole.

Gravid Traps:
Gravid trap activity is reflecting a declining mosquito population as the weather cools down substantially. Trap counts are especially lower this week in the towns of Dedham, Norwood, and Westwood. Unusually high numbers are reported in Avon and Milton, but this is due to Oc. japonicus activity rather than that of Culex pipiens/restuans.

2. Current Predominant Species

The most predominant mosquito species in CDC traps are Ae. vexans with populations that spiked in the above towns. There appears to be a boost in Oc. trivittatus activity in towns with VEX-associated spikes. Ochlerotatus canadensis populations are declining. Recent rain events have also presented a slight rise in Culiseta melanura numbers in Sharon light traps situated nearby the cedar swamp. Gravid traps are dominated by Cx. pipiens/restuans still, though the population is in a state of decline. Oc. japonicus populations have climbed in a few towns, especially in gravid traps with few Cx. pipiens/restuans.

3. Comparison to previous season

In general, CDC activity this week is the same compared to last season except for Bellingham, Canton, Dedham, Franklin, Millis, Norfolk, and Walpole due to unusually higher than average Ae. vexans and Oc. trivittatus populations. Gravid trap mosquito activity this week is generally the same as last season’s numbers but there is much lower activity in the towns of Dedham, Norwood, and Westwood. Higher than normal activity is noted in Avon and Milton, but this is due to increased Oc. japonicus activity rather than that of Cx. pipiens/restuans. Of note is the trend towards cooler evening/morning temperatures which will no doubt affect trap collections.

4. Weather Summary

Monday featured some leftover showers early in the morning from the prior weekend rains. A cold frontal passage on Wednesday brought widespread showers and thunderstorms to the county, followed by some light rainfall on Thursday morning as a low developed along the front. Total rainfall ranged from around a half inch in the north, to pockets of over an inch along the southern county boundary. The remainder of the week was dry. Temperatures early in the week were slightly above normal, then slightly below normal after the frontal passage.

Total weekly rainfall: 0.87 inches (+0.28 in.)
Total Monthly rainfall: Sept: 7.21 inches (+3.74 in.), Oct: 0.79 inches (+0.32 in)
Total Yearly rainfall: 41.02 inches (+9.37 in.)

5. Number of requests for service

NCMCP has discontinued the recording of calls for early morning ULV applications.

6. MCP/Commission response

NCMCP has discontinued “area wide” ground ULV applications effective Friday, September 12, 2008 due to predicted long range weather conditions that will not be conducive to effective applications. Coordination between NCMCP and the local Boards of Health is ongoing relative to interpretation of surveillance results and how best to get the word out to the public relative to avoidance of mosquito bites. NCMCP remains prepared to conduct additional ground adulticide activities if required.


144 Production Rd, Suite C

Walpole, MA 02081

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