Week 30 – July 22 – 23

2008 Mosquito Report: Week 30

Report based on data collected from traps deployed on Tuesday, July 22, 2008 and retrieved on Wednesday, July 23, 2008. Report prepared by John Smith, Chan Suom, M.S., and Nate Boonisar.

1. Current mosquito activity/trend

CDC Light Traps:
For the most part, CDC activity is down this week compared to last year’s data for host-seeking mosquitoes. The most predominant CDC trapped mosquitoes were once again Coquillettidia perturbans. Towns experiencing an increase in host seeking mosquito activity showed an increase in Culiseta melanura presence. This can be seen especially around the Great Black Swamp located in Millis and Medway which is comprised of, among others, cedar trees, habitat for Cs. melanura. The Medway trap in particular showed a dramatic increase in Culiseta melanura numbers. There is some evidence of an emergence of summer refloods across the county, specifically Aedes vexans. Some Ocherlotatus canadensis are also present but in low numbers. Although not reflected in trap data, service requests and site visits in the City of Quincy and North Weymouth continue to indicate a presence of salt marsh mosquitoes (Ochlerotatus sollicitans) in coastal areas.

Gravid Traps:
Gravid traps in most towns have either retained their level of activity or have increased such as in the towns of: Avon, Bellingham, Canton, Dedham,Dover, Foxboro, Holbrook, Medfield, Medway, Needham, Norfolk, Plainville, Quincy, Randolph, and Stoughton. The highest numbers of Culex pipiens/restuans collected in the traps continue to be located in the eastern third of the county with only a few notable exceptions (Medway & Bellingham). Ochlerotatus japonicus populations are slowly increasing compared to last week’s and last year’s numbers.

2. Current Predominant Species

The most predominant CDC trapped mosquitoes were once again Coquillettidia perturbans. Medway showed a dramatic increase in Culiseta melanuranumbers. Aedes vexans populations continue to be collected across the county due to recent rain events.

3. Comparison to previous season

CDC activity is down this week compared to last year’s data for mammal biting mosquitoes with a few exceptions relative to Coquillettidia perturbanscollections in central and western trap sites. There were numerous thunderstorm/rain events that have resulted in this season’s first significant presence of Aedes vexans in Canton. Gravid trap activity remains steady at levels close to or above the average.

4. Weather Summary

A slow moving cold front, combined with a strong southerly flow of tropical moisture produced widespread heavy rain and thunderstorms throughout NorfolkCounty this week. While local amounts were highly variable, a general 2.5 to 5 inches of rain fell county-wide, with lowest amounts in the extreme south, and highest amounts in three bands located across the northwest, east-central, and far eastern sections. See attached precipitation contour map for more details.

Due to antecedent dry conditions, this rainfall did not produce flooding on the main rivers in the County; however, river levels are running above normal for this time of year. This rain, combined with prior weeks’ rain, has put a significant dent in longer term dryness, nearly eliminating any deficits. Both 60 and 90-day rainfall has been between 90 and 110% of normal county-wide (with the exception of the extreme south at 75% of normal, and the extreme north, 125-150% of normal).

Total weekly rainfall: 3.20 inches (+2.51 in.)
Total Monthly rainfall: 5.44 inches (+2.88 in)
Total Yearly rainfall: 26.95 inches (+3.12 in.)

5. Number of requests for service

Year to date NCMCP has received 2,607 calls for service as of 7/26/08. This represents a total of 260 calls for the week. This shows a significant decrease in calls from last year. Last year at this time the calls for service (year to date) were 4,196. Year to date for 2006 NCMCP had received 4,827 calls for service by the same date. Compared to the last two years, calls are running much lower this year.

6. MCP/Commission response

In general our response has been to continue ground ULV applications targeting areas of high public demand. NCMCP is making good progress toward treating rain basins in highly urban areas where Culex pipiens/restuans activity is highest. Most of the rain basins in highly urban areas in the eastern half of the county have been treated at this point.


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