Week 31 – July 29 – 30

2009 Mosquito Report: Week 31

Report based on data collected from traps deployed on Wednesday, July 29, 2009 and retrieved on Thursday, July 30, 2009. Report prepared by John Smith, Chan Suom, M.S., and Nate Boonisar.

1. Current mosquito activity/trend

CDC Light Traps:
Host-seeking mosquito activity was higher than average in most of Norfolk County, with only the long term Walpole trap site reporting lower than average mosquito activity. The towns of Bellingham, Franklin, Holbrook, Needham, Plainville, Quincy, and Weymouth experienced average levels of host-seeking mosquito activity.

Gravid Traps:
Following last week’s trend, all of the towns in Norfolk County experienced yet another lower than average trap collection.

2. Current Predominant Species

CDC Light Traps:
The most predominant CDC trapped mosquitoes this week was once again Coquillettidia perturbans, which was noted in most towns in NorfolkCounty. There was a boom in Oc. canadensis populations in the towns of Foxboro, Norfolk, and Sharon. Psorophora ferox populations are still higher than average in Canton. Ae. vexans populations are high in sporadic parts of the county but there are no successively greater numbers since the first mass emergence noted a few weeks back. Culex pipiens/restuans populations are high in Braintree, Canton, Foxboro, Medway, Milton, and Wrentham in our CDC traps.

Gravid Traps:
Gravid traps collections remain dominated by Culex pipiens/restuans. Oc. japonicus populations are average. There was an unusually high collection of 23 An. punctipennis mosquitoes at Eastern Avenue in Dedham. Beavers have created a large flooded area adjacent to this trap site. This may be the reason for higher Anopheles collections.

3. Comparison to previous season

Host-seeking mosquito activity this week was mostly higher than average due to the continued activity of Co. perturbans. Oc. canadensis populations continue to be high especially around the cedar swamp in Sharon. Isolated populations of Culex pipiens/restuans remain strong in some parts of the county. Ps. ferox populations continue to be unusually high in Canton. In general, gravid trap collections for Norfolk County are lower than average. This reflects a continuation of last week’s lower collection trend.

4. Weather Summary

This week was warm and humid. Cold frontal passages later in the week brought showers and thunderstorms to the area, with heavier totals in the west. Weekly rainfall ranged from ½ inch in the east, to locally nearly 2 inches in the extreme western sections. For the month of July, precipitation across most of the county was nearly double the normal amount.

Total weekly rainfall: 0.82 inches (+0.12 in.)
Total Monthly rainfall: 7.03 inches (+3.97 in.)
Total Yearly rainfall: 26.81 inches (+2.37 in.)

5. Number of requests for service

NCMCP received 3,584 calls for service as of 7/31/09. NCMCP received 450 calls for service this week.

6. MCP/Commission response

NCMCP continues to conduct “area wide” ground ULV applications in areas of high calls; where virus has been identified or where light trap/landing count collections dictate additional applications. Due to an increase in demand these ULV activities have been expanded across the county again this week. NCMCP continues treatments to rain basins in high density basin areas such as centers of towns although these activities have been interrupted from time to time due to redeployment of field staff to other ground larvicide activities. Field staff treated areas on the salt marshes due to high monthly tides and rain events this week. We expect an emergence of salt marsh mosquitoes in the next week or so.

NCMCP will deploy additional gravid traps and CDC light traps in select areas of Walpole proximate to the DPH site early next week. NCMCP conducted area wide ULV applications in areas proximate to this positive WNv collection. Coordination between NCMCP and all local Boards of Health is ongoing relative to interpretation of surveillance data 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, ground larvicide and aerial larvicide control activities as required.


144 Production Rd, Suite C

Walpole, MA 02081

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