Week 33 – Aug 15-19

2011 MOSQUITO REPORT: WEEK 33

Report based on data collected from traps deployed the week of August 15, 2011 through August 19, 2011. Report prepared by John Smith, Chan Suom, M.S., and Nate Boonisar.

1. CURRENT MOSQUITO ACTIVITY/TREND

CDC Light Traps:
Host-seeking activity throughout Norfolk County continues the trend of low collections for another week. Except for Foxboro, Walpole, and Weymouth, all other towns collected lower than average numbers of host-seeking mosquitoes from their traps.

Gravid Traps:
Gravid trap collections are mixed this week. The towns of Avon, Dover, Franklin, Medway, Norwood, Quincy, Randolph, Stoughton, and Westwood returned higher than average numbers of gravid mosquitoes, whereas Bellingham, Braintree, Dedham, Foxboro, Holbrook, Millis, Milton, Plainville, Sharon, and Wrentham reported the opposite. The remaining towns’ traps indicated normal levels of mosquito activity.

2. CURRENT PREDOMINANT SPECIES

CDC Light Traps:
Culiseta melanura continues to be very populous in Holbrook and parts of Sharon. Coquillettidia perturbans numbers continue to decline. Host-seeking activity was generally low throughout the county, so there isn’t much of a reference to make. On the other hand, we expect a higher number of Aedesvexans and Ochlerotatus canadensis in next week’s trap collections due to the recent streak of rain events.

Gravid Traps:
Gravid Culex pipiens/restuans mosquito populations are mixed for this week. Oc. japonicus numbers are about average.

3. COMPARISON TO PREVIOUS SEASON

The continued scattered thunderstorms and low overnight temperatures (low 50’s) during our trapping period seems to have mostly hindered host-seeking mosquito activity this week. An interesting observation is the increase of Cs. melanura populations that has coincided with the previous weeks’ trend of steady rain events, which may likely be creating plentiful Cs. melanura habitat within the wetlands crypts. Landing counts conducted near flood plains have already indicated localized population boons of Ae. vexans as a result of recent rain events, so we reluctantly expect much more in our traps in the following weeks.

4. WEATHER SUMMARY

The above normal trend in precipitation continued this week. A coastal storm on Monday produced a widespread one to two inches of rain county-wide. This was not enough to produce any widespread river flooding but continued to add to an above normal water table. More thunderstorms on Friday brought up to one half inch of rain to mainly western sections. August precipitation now ranges from 150% to 300% of normal from east to west.

Total weekly rainfall: 1.26 inches (+0.49 in.)
Total Monthly rainfall: 5.16 inches (+3.02 in.)
Total Yearly rainfall: 29.62 inches (+3.15 in.)

5. NUMBER OF REQUESTS FOR SERVICE

NCMCP received 6,446 calls year to date for service as of 8/20/10. NCMCP received 406 calls for service this week.

6. MCP/COMMISSION RESPONSE

NCMCP continues ground ULV applications in high request areas and in areas where collection data indicate a need. ULV applications have been reduced proportionate to the decline in requests for service. Rain basin treatments continue with a concentration in urban areas where West Nile virus (WNV) has been collected. NCMCP is also prioritizing basin treatments adjacent to areas in Boston where West Nile virus has been identified. NCMCP continues some ground larviciding in certain areas in response to flooding due to frequent rain events. Due to the positive WNV isolates in mosquitoes collected in Dedham, Dover, Holbrook, Needham, Norwood, Quincy and Westwood, NCMCP has conducted localized (focused) applications of both ULV and rain basin treatments. Boards of Health in all communities have stepped up public outreach using all available local media outlets. There is evidence of an emergence of Aedes vexans (and perhaps other summer reflood species) in the Dedham area. Swarms of mosquitoes have been observed and aspirated mosquitoes collected in this area have confirmed these to be Aedes vexans.

Contact

144 Production Rd, Suite C

Walpole, MA 02081

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