Week 34 – Aug 22-26

2011 MOSQUITO REPORT: WEEK 34

Report based on data collected from traps deployed the week of August 22, 2011 through August 26, 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 most of Norfolk County experienced a surge mainly due to previous rain events. Avon, Braintree, Foxboro, Medfield,Stoughton, parts of Walpole, and parts of Weymouth returned average collections, whereas Medway, Milton, Quincy, and parts of Sharon collected lower than average numbers of mosquitoes.

Gravid Traps:
Gravid trap collections are mostly average to below average for the week. Only Dover, Medway, Walpole, and Weymouth collected higher than average numbers of gravid mosquitoes.

2. CURRENT PREDOMINANT SPECIES

CDC Light Traps:
Culiseta melanura continues to be very populous in Holbrook and parts of Sharon. Coquillettidia perturbans had isolated population surges in Bellingham,Canton, Millis, and Norfolk. Another benefactor from the recent rain events is Aedes vexans, as their populations were higher than average in Bellingham,Canton, Dedham, Franklin, Millis, Needham, Walpole, Weymouth, and Wrentham. Anopheles walkeri had an unexpected higher than average collection inFranklin, whereas Ochlerotatus trivittatus appeared in higher than average numbers in Walpole. Culex pipiens/restuans populations were higher than average in Franklin.

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 seemingly weekly rain and thunderstorm events have created plenty of habitat for flood-type mosquitoes as seen from this week’s collection records. There are plenty of newly emerged Ae. vexans and Co. perturbans due to these events. It appears as though a steady, rainy season has coincided with a higher than usual Cs. melanura population. We’ve yet to see if Hurricane Irene’s flooding will negatively affect Cs. melanura numbers by washing them away from the safety of their crypt habitats. We expect this newly abundant population of Ae. vexans to last at least another week.

4. WEATHER SUMMARY

Other than some showers early in the week, the main weather story was Hurricane Irene. Rainfall from the storm came in two waves: a predecessor rainfall event on Saturday that affected mainly far western sections with up to 3 inches, and the main storm event on Sunday. There was a sharp cutoff in rainfall totals that ran roughly along Interstate 95. To the east, between one and two inches fell, while to the west, two to six inches of rain fell. Amounts over five inches were confined to Needham, Dover, and Westwood, as well as Millis, Medway, and Bellingham. This caused significant rises on the Charles River, bringing it within two feet of flood stage. This level would likely have inundated large areas of the forested flood plain. On the Neponset, there were also significant rises that likely inundated large portions of its flood plain as well. In addition, rainfall this month has ranged from 6 inches in the east, to nearly 14 inches in the west. A U.S. Geological Survey well in Norfolk indicates ground water levels are now equal to normal springtime levels.

Total weekly rainfall: 3.82 inches (+2.93 in.)
Total Monthly rainfall: 8.98 inches (+5.95 in.)
Total Yearly rainfall: 33.44 inches (+6.07 in.)

5. NUMBER OF REQUESTS FOR SERVICE

NCMCP received 6,740 calls year to date for service as of 8/26/11. NCMCP received 434 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. 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 Bostonwhere 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 areas adjacent to both the Charles and Neponset River basins. Swarms of adult mosquitoes have been observed in both locations which have been mainly identified as Aedes vexans although other reflood species have also been observed.

Contact

144 Production Rd, Suite C

Walpole, MA 02081

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