Week 38 – Sept 17 – 18

2008 Mosquito Report: Week 38

Report based on data collected from traps deployed on Wednesday, September 17, 2008 and retrieved on Thursday, September 18, 2008. Report prepared by John Smith, Chan Suom, M.S., and Nate Boonisar.

1. Current mosquito activity/trend

CDC Light Traps:
Although a decline continues in CDC mosquito activity across the county, Canton (vexans) and Wrentham (canadensis) collected higher mosquito numbers compared to last week.

Gravid Traps:
Gravid trap mosquito activity has picked up substantially from last week and is evidenced in the following towns: Bellingham, Canton, Dedham, Dover, Franklin, Holbrook, Medway, Millis, Milton, Needham, Norwood, Quincy, Randolph, Sharon (NS), Walpole, and Westwood. This could reflect either an increase in population or better trap night weather conditions from week 37 to week 38. The overall trend continues to show a downward trend from the season’s highs.

2. Current Predominant Species

The most predominant mosquito species in CDC traps are Ochlerotatus canadensis and Aedes vexans, although their numbers are relatively low compared to previous weeks. Gravid traps are dominated by Cx. pipiens/restuans still. Ochlerotatus 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 this season compared to last season except for Canton and Wrentham. Gravid trap mosquito activity this week is generally higher than last season’s numbers and it breaks the declining trend from the past couple of weeks. NCMCP anticipates an increase in reflood species, especially Aedes vexans, as a result of heavy rains which fell a while ago associated with tropical system Hanna. This may not be reflected in the CDC traps due to cooler trap night temperatures.

4. Weather Summary

The only rain to fall this week was on Sunday the 14th when a warm front brought a widespread ¼ to ½ inch of rain to the county, as well as warm weather on Monday. A cold frontal passage later on Monday and again Wednesday dropped temperatures below to much below normal by the end of the week. A somewhat drier pattern has emerged over the last couple weeks with rainfall running 25-75% of normal, however, 1 to 3 month rainfall amounts have generally averaged near normal to above normal county-wide.

Total weekly rainfall: 0.43 inches (-0.27 in.)
Total Monthly rainfall: 3.54 inches (+1.24 in.)
Total Yearly rainfall: 36.55 inches (+6.55 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

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