Week 34 – Aug 23 – 27

2010 Mosquito Report: Week 34

Report based on data collected from traps deployed the week of August 23, 2010 through August 27, 2010. Report prepared by John Smith, Chan Suom, M.S., and Nate Boonisar.

1. Current mosquito activity/trend

CDC Light Traps:
Most CDC light trap collections indicated a return to average levels of host-seeking mosquito activity throughout Norfolk County. Only Franklin reported a higher than average collection whereas Avon, Canton, Medway, Millis, Milton, Sharon, and parts of Walpole showed a decline in the catch.

Gravid Traps:
Contrary to last week’s higher than average collections, most town traps reported a lower than average gravid mosquito population. Only Franklin and Norwoodcollected higher than average numbers of gravid mosquitoes whereas Braintree, Foxboro, Franklin, Medway, Norfolk, Norwood, and Stoughton only collected average numbers.

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 relatively low collections compared to the historical average. A recent emergence of Ochlerotatus sollicitans in the northeastern portion of the county is reflected in this week’s trap collections and service request calls from Quincy.

Gravid Traps:
Culex pipiens/restuans populations are lower 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 cooler overnight temperatures during our trapping schedule. Container breeders and permanent water body species are the most common collections in our traps. WNv has been been detected within Norfolk County for the first time this season in the town of Dedham from last week’s specimens submitted for testing. Although host-seeking populations are low, EEE andWNv continue to be isolated in or around the borders of Norfolk County. Gravid mosquito activity has returned to a state of population decline, most likely due to the cooler evening temperatures during the trapping schedule.

4. Weather Summary

A slow moving storm system brought copious amounts of rain to the area during the first half of this week. Amounts over the period ranged from 2 inches in the west to over 6 inches in the east (Blue Hill observatory received 7.59” due to a localized orographic effect). Please see amounts below from Norfolk County towns as reported to the National Weather Service in Taunton. Due to the prolonged nature of rainfall and antecedent dry conditions, significant river flooding was not an issue but the Neponset and Charles Rivers did experience some short term spikes which may have flooded localized areas of their flood plains. However, the soaking rain likely replenished low water tables to create some wetland re-flooding, especially in eastern sections. While this rainfall made a significant dent in the long term dryness, the USDA drought monitor continues to designate the entire county as “abnormally dry;” however, the data for this ranking was compiled before the heavy rains of Tuesday and Wednesday. 30-day rainfall is now above normal for most of the county except for the extreme southwest section (75% of normal), 60-day rainfall is above normal in only the northeast section, with near to slightly below normal over the remainder of the county, and 90-day rainfall is near normal in the northeast to 50-75% of normal in the southwest.

Total weekly rainfall: 4.12 inches (+3.34 in.)
Total Monthly rainfall: 4.67 inches (+1.64 in.)
Total Yearly rainfall: 35.46 inches (+8.09 in.)

5. Number of requests for service

NCMCP received 6,682 calls year to date for service as of 8/27/10. NCMCP received 237 calls for service this week.

6. MCP/Commission response

In most of the county, NCMCP ground ULV applications continue but at a low level. Overall complaints from residents (year to date) continue at levels higher than in the past three years although this weeks numbers were down most like as a result of the poor weather conditions. 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 Bs as the active ingredients. 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. As reported above, the two gravid trap sites in the Town of Dedham have collected West Nile Virus positive mosquitoes. NCMCP is coordinating with the Dedham Health Department adult control applications in these areas. The Dedham Board of Health is pursuing all means of public outreach including an article in the local paper. NCMCP, as part of the adult control applications, will treat several large sports complexes within the WNV active area ofDedham. Heavy rains (as detailed above) in the eastern third of the county resulted in some minor flooding which most likely will produce an emergence of summer refloods on or about Labor Day. Much of the surface water flooding was light and may dry up before producing significant reflood populations. NCMCP does not anticipate a large “county wide” emergence. NCMCP will dispatch field crews to treat rain induced salt marsh larval development inQuincy and Weymouth.


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Walpole, MA 02081

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