Week 25 – June 21 – 25

2010 Mosquito Report: Week 25

Report based on data collected from traps deployed the week of June 21, 2010 through June 25, 2010. Report prepared by John Smith, Chan Suom, M.S., and Nate Boonisar.

1. Current mosquito activity/trend

CDC Light Traps:
Most towns in Norfolk County experienced a surge in mosquito activity such as the following: Avon, Bellingham, Braintree, Canton, Franklin, Holbrook, Medway, Millis, Milton, Norfolk, parts of Sharon, parts of Walpole, and Wrentham. Medfield was the only town to record lower than average mosquito activity. Dedham, Foxboro, Needham, Plainville, and Weymouth reported average mosquito populations.

Gravid Traps:
Gravid traps were deployed for the first time this season. Most towns in the county reported average mosquito activity. Avon and Randolph had lower than average collections. The towns of Bellingham, Dedham, Holbrook, Medfield, Medway, Milton, Quincy, and Walpole recorded higher than average numbers of mosquitoes.

2. Current Predominant Species

CDC Light Traps:
The most predominant CDC trapped mosquitoes in Norfolk County this week were once again Coquillettidia perturbans. As in recent weeks, Ochlerotatus canadensispopulations are on the decline. Culex pipiens/restuans have become numerous in light traps in Franklin and Medway.

Gravid Traps:
Culex pipiens/restuans dominate gravid trap collections. It appears Oc. triseriatus populations are increasing as they are almost as common in gravid traps as Oc.japonicus.

3. Comparison to previous season

Mosquito activity is higher than average in most towns in Norfolk County. Coquillettidia perturbans populations continue last week’s trend of spiking in many parts of the county. Every CDC light trap has a collection of Co. perturbans. Avon collected over 1300 specimens, whereas Franklin collected a little under 2000. The Millis and Walpole traps collected more than 2000 Co. perturbans respectively. We are not sure if this is the peak of their activity but will continue to monitor this species closely in future collections. If the previous weeks are any indication, this trend may just continue into Week 26, the historical peak of Co. perturbansin Norfolk County.

4. Weather Summary

A weak cold frontal passage on Sunday brought thunderstorms to the area. Rainfall was highly variable ranging from a trace to nearly 1.5 inches in localized spots, mostly in the north and south. A warm frontal passage on Tuesday night into Wednesday brought some light rain to the area, with amounts averaging from a trace to ¼ inch. Finally a cold frontal passage on Thursday brought more thunderstorms, mainly in the northern part of the county with amounts up to ¼ inch. Overall for the week, rainfall was near to slightly below normal across most of the county (except for localized areas with well above normal precip), with well below normal amounts in the far west. Monthly rainfall continues below normal county-wide. Meanwhile temperatures were well above normal all week.

Total weekly rainfall: 0.55 inches (-0.20 in.)
Total Monthly rainfall: 2.18 inches (-0.62 in.)
Total Yearly rainfall: 29.61 inches (+8.75 in.)

5. Number of requests for service

NCMCP received 2,975 calls year to date for service as of 6/25/10. NCMCP received 368 calls for service this week.

6. MCP/Commission response

NCMCP has been conducting “area wide” ground ULV applications when and where necessary. Rain basin monitoring with a Landers Ladle indicatedCulex larvae present in many of the basins sampled and at a higher rate than in Epi week 24. As a result NCMCP has begun rain basin treatments using a briquette with both Bti and Bs as the active ingredients (Fourstar). Interesting note – the larvae collected from an pre-installed (above ground) rain basin chamber at one of the eastern most DPW sites were identified as Ochlerotatas altropalpus, commonly referred to as the rock pool mosquito.


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Walpole, MA 02081

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