Week 28 – July 8 – 9

2009 Mosquito Report: Week 28

Report based on data collected from traps deployed on Wednesday, July 8, 2009 and retrieved on Thursday, July 9, 2009. 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 lower than average host-seeking mosquito activity compared to previous years due, in part, to sporadic thunderstorms and cool nights during our trapping schedule. The towns of Avon, Canton, Medway, and Quincy recorded higher than average host-seeking mosquito activity primarily due to spikes in the Coquillettidia perturbans population.

Gravid Traps:
All towns in Norfolk County experienced lower than average gravid mosquito activity. This may be primarily due to the sporadic rain- and thunder-storms that interrupt the surface of the water and/or flooding the gravid traps, preventing our traps from collecting a representative sample this week.

2. Current Predominant Species

The most predominant CDC trapped mosquitoes this week were Coquillettidia perturbans once again. Our first significant Aedes vexans (1300+) population was observed in the town of Canton. Oddly enough, there were spikes in Culex pipiens/restuans host-seeking populations in Canton, Medway, and Quincy. Quincy reported a higher than average Aedes sollicitans population for the first time this season. Though their numbers are uncharacteristically low, Culex pipiens/restuans are the most abundant species in gravid traps. Ochlerotatus japonicus gravid populations were almost non-existent this week. Further field observations on 07/10/09 indicated a staggered hatch of summer refloods (mostly Ae. vexans) in the Neponset River floodplain is continuing although water levels have receded considerably. At the Neponset River floodplain sites visited (Canton and Norwood) dipping in the remaining pockets of stagnant water showed mostly fourth instars and pupae (@10 per dip) with a few third instars. There was no evidence of new eggs hatching as a result of rain events this week. Fortunately the Charles River floodplain has remained well below flood stage as witnessed during site visits in Millis, Medfield and Dover. Adults were numerous at all sites visited. Site visits in the Medway area just south of Hopkinton, where street flood occurred this week, showed no additional flooding. As a side note, higher numbers of Tabanids (mainly deer flies) were observed at all sites visited.

3. Comparison to previous season

Except for the few towns with spikes in Coquillettidia perturbans activity, host-seeking activity was very low across the remainder of Norfolk County. Ovipositing mosquito activity was also low this week when compared to last year’s and last week’s figures. Once again, due to inclement weather conditions, most towns did not experience typical mosquito activity. On a side note, as predicted from last week’s report, we observed our first Aedesvexans spike with more than 1300 specimens in one trap (Canton). With fair weather predictions, we expect more surges in Aedes vexans populations this upcoming week.

4. Weather Summary

The showery and below normal temperature pattern continued this week, however, there was more sunshine with slightly higher temperatures than previous weeks. The main precipitation fell on Tuesday and Wednesday. Most of the county received between 0.5 and 0.75 inches of rain on Tuesday (with local amounts to one inch), while a localized thunderstorm produced over a ½ inch of rain across far western sections on Wednesday. So far this month, the entire county has received much above normal rainfall with many areas equaling or exceeding the normal rainfall for the entire month of July. Overall, yearly rainfall is between 90%-110% of normal county-wide.

Total weekly rainfall: 0.91 inches (+0.22 in.)
Total Monthly rainfall: 2.87 inches (+1.77 in.)
Total Yearly rainfall: 22.65 inches (+0.28 in.)

5. Number of requests for service

NCMCP received 1,864 calls for service as of 7/10/09. NCMCP received 415 calls for service this week.

6. MCP/Commission response

NCMCP has been conducting “area wide” ground ULV applications in areas of high calls or where light trap/landing count collections dictate additional applications. NCMCP began treating rain basins the first week of June although these activities have been interrupted from time to time due to redeployment of field staff to other ground larvicide activities associated with treatments targeting heavy rain event flooding. Coordination between NCMCP and the local Boards of Health is ongoing relative to interpretation of surveillance data and how best to get the word out to the public relative to avoidance of mosquito bites. NCMCP remains prepared to conduct additional ground adulticide, ground larvicide and aerial larvicide control activities as required.


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Walpole, MA 02081

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