Week 31 – July 30 – 31

2008 Mosquito Report: Week 31

Report based on data collected from traps deployed on Wednesday, July 30, 2008 and retrieved on Thursday, July 31, 2008. Report prepared by John Smith, Chan Suom, M.S., and Nate Boonisar.

1. Current mosquito activity/trend

CDC Light Traps:
While the towns of Canton, Franklin, and Medway experienced higher mammal biting mosquito activity, CDC trap activity across the county was down once again compared to last year’s data. The most predominant CDC trapped mosquitoes were once again Coquillettidia perturbans. As somewhat reflected in trap data, service requests and site visits in the City of Quincy and North Weymouth, salt marsh mosquitoes (Ochlerotatus sollicitans) are an annoyance in coastal areas. The most recent brood seems to be rain induced rather than tidal.

Gravid Traps:
Gravid traps in most towns have retained their level of activity and increased activity (compared to last week) can be seen in the following towns: Braintree, Dover, Foxboro, Franklin, Holbrook, Sharon, and Weymouth. Ovipositing mosquito activity is higher this week when compared to last year’s figures. In general gravid trap collects seem to be declining but most collections still remain above the multi-year average. The highest numbers of Culex pipiens/restuans collected in the traps continues to be located in the eastern third of the county. 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 although the numbers collected have been declining in most locations following a typical bell shaped curve. Uranotaenia sapphirina has made a significant appearance so far this season, whereas Culiseta melanuraactivity is lower when compared to last week and last year’s figures.

3. Comparison to previous season

CDC activity is down in general this week compared to last year’s data. There have been numerous thunderstorm/rain events in past weeks that have resulted in sporadic collections of Aedes vexans although the numbers collected have begun to decline. Gravid trap activity has declined somewhat but remains close to or above the average at most trap sites across the county.

4. Weather Summary

This week started out with a couple rounds of showers and thunderstorms on Sunday that gave around 0.25” in the east to 1.25” in the west. The remainder of the week was dry with temperatures near normal for this time of year. An area of weakening thunderstorms gave some light rainfall on Thursday with no areas receiving more than 0.10” of rain. Finally, more rounds of showers and thunderstorms on Saturday provided anywhere from a trace of rain in the west, to up to an inch of rain in the east. County-wide for the week, rainfall ranged from 0.75” to 1.50” which continues our 30 and 60-day trend of near normal to above normal rainfall.

Total weekly rainfall: 1.26 inches (+0.56 in.)
Total Monthly rainfall: July: 6.19 inches (+3.13 in.), August: 0.51 inches (+0.31 in.)
Total Yearly rainfall: 28.60 inches (+4.06 in.)

5. Number of requests for service

Year to date NCMCP has received 2,870 calls for service as of 8/2/08. This represents a total of 268 calls for the week. The weekly calls for service seem to be holding steady at @ 260. Last year at this time the calls for service (year to date) were 4,479. Year to date for 2006 NCMCP had received 5,268 calls for service by the same date. Compared to the last two years, calls are running much lower this year most likely due to higher levels of human biting mosquitoes in 2006 and 2007 as well as elevated EEE isolations in mosquitoes by this time in the previous two years.

6. MCP/Commission response

In general our response has been to continue ground ULV applications targeting areas of high public demand. NCMCP has just about completed treatments of rain basins in all urban areas. In Epi Week 32 additional trapping of gravid Culex pipiens/restuans will take place in the vicinity of WNv positive bird locations. Gravid trap placement before and after an early morning ULV application in the area of the Needham WNv positive mosquito pool showed a substantial depression of Culex pipiens/restuans numbers as compared to the two closest gravid trap sites in areas which were not treated.

Contact

144 Production Rd, Suite C

Walpole, MA 02081

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