Week 33 – Aug 16 – 20

2010 Mosquito Report: Week 33

Report based on data collected from traps deployed the week of August 16, 2010 through August 20, 2010. Report prepared by John Smith, Chan Suom, M.S., and Nate Boonisar.

1. Current mosquito activity/trend

CDC Light Traps:
Norfolk County CDC light trap collections continue to indicate a mix of below average to average host seeking mosquito activity. Compared with last week’s collections, mosquito activity is holding steady, albeit in low numbers.

Gravid Traps:
Gravid mosquito activity across Norfolk County has dramatically increased from recent weeks (perhaps due to the August 5th rain event). Towns that reported higher than average gravid mosquito activity included: Bellingham, Braintree, Dedham, Franklin, Medway, Millis, Milton, Needham, Norfolk, Norwood, Plainville,Quincy, parts of Sharon, Westwood, Weymouth, and Wrentham. Avon, Canton, Dover, Foxboro, Medfield, Randolph, Stoughton, and Walpole have returned to average collection numbers. Only Holbrook and parts of Sharon reported lower than average gravid mosquito collections.

2. Current Predominant Species

CDC Light Traps:
The most predominant CDC-trapped mosquito in Norfolk County this week is once again Coquillettidia perturbans, but all indications point to relative low collections compared to the historical average. Most specimens appeared aged. Culex pipiens/restuans and Anopheles walkeri populations continue to be higher than average in Franklin. Uranotaenia sapphirina populations are becoming more common as is normal at this time of the season. The lack of rain events has left wetlands dry and has favored container-breeding and permanent water species.

Gravid Traps:
Culex pipiens/restuans populations have spiked this week throughout all of Norfolk County. Ochlerotatus japonicus numbers are average.

3. Comparison to previous season

Host-seeking mosquito activity continues to be low into this week. The primary factor affecting this is the lack of rain events, which has left wetlands dry. Container breeders and permanent body species are the most common collections in our traps. Although host-seeking populations are low, EEE and WNv continue to be isolated around the borders of Norfolk County. Gravid mosquito activity has taken a turn, reflecting a population boost from previous weeks. This may be due to an August 5th rain event which was enough to replenish permanent-water and container-breeding mosquito habitats, but not enough to create habitat for vernal pool or flood dependent species.

4. Weather Summary

Weather conditions continued to be similar to previous weeks this summer. Temperatures were above normal with humidity to start. A cold front brought some showers and thunder to the area on Monday with amounts generally between a tenth and quarter inch (highest in the south). Otherwise, sunny and somewhat cooler (at night) and drier towards the end of the week.

Total weekly rainfall: 0.08 inches (-0.69 in.)
Total Monthly rainfall: 0.55 inches (-1.70 in.)
Total Yearly rainfall: 31.34 inches (+4.76 in.)

5. Number of requests for service

NCMCP received 6,446 calls year to date for service as of 8/20/10. NCMCP received 406 calls for service this week.

6. MCP/Commission response

NCMCP ground ULV applications continue but at a low level. NCMCP has seen an increase in complaints from the typical residential areas adjacent to salt marshes (East Quincy and North Weymouth). Overall the complaints remain the highest since 2007 and continue to be sustained at an “elevated” level this week due to the recent salt marsh emergence and media (EEE & WNv) induced calls. NCMCP is wrapping up treatments of rain basins in the highly urban areas (especially in the eastern half of the county) using a pouch with Bacillus sphaericus as the active ingredient. Concern is mounting along the eastern edge of the county due to an increase in WNv isolates in the bordering communities of Newton, Brookline and Boston. Our concern with WNv is further fueled by a fairly dramatic spike in gravid trap collections (Culex) in the towns of Dedham, Norwood, Needham and Milton which border these WNv active areas.


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Walpole, MA 02081

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