Week 30 – July 22 – 23

2009 Mosquito Report: Week 30

Report based on data collected from traps deployed on Wednesday, July 22, 2009 and retrieved on Thursday, July 23, 2009. Report prepared by John Smith, Chan Suom, M.S., and Nate Boonisar.

1. Current mosquito activity/trend

CDC Light Traps:
Host-seeking mosquito activity was inconsistent throughout Norfolk County. The towns of Avon, Canton, Dedham, Foxboro, Holbrook, Millis, Milton,Quincy, Sharon, and Wrentham experienced higher than average host-seeking mosquito activity whereas Franklin, Needham, Medway, Walpole, andWeymouth experienced lower than average levels of mosquito activity. The towns of Bellingham, Braintree, Medfield, Norfolk, and Plainville reported average levels of mosquito activity.

Gravid Traps:
Gravid mosquito activity, for the most part, was lower than average across all of Norfolk County except for Franklin and parts of Sharon. The general trend across the county has been a fairly dramatic drop. Since weather conditions for the trap night were favorable could this drop be due to excessive rainfall and the effect this “recharge” has on Culex larval habitats?

2. Current Predominant Species

CDC Light Traps:
The most predominant CDC trapped mosquitoes this week were once again Aedes vexans and Coquillettidia perturbans. Psorophora ferox populations have remained high in Canton, with more numbers than last week. Coquillettidia perturbans collections have slipped off their peak which seems to have occurred around week 28 at most trap sites. Oc. canadensis collections have spiked at several trap locations with higher populations in Foxboro, Sharon, Walpole, and Wrentham. Culiseta melanura collections went from 20 last week to 180 this week in the Holbrook CDC Light trap, a nine fold increase. The Holbrook Trap has a history of collecting EEE positive Cs. melanura. Culex pipiens/restuans populations in our CDC traps are high in Dedham, Holbrook, Medway, Walpole, Wrentham, and Quincy.

Gravid Traps:
Gravid traps are collecting predominately Culex pipiens/restuans. Oc. japonicus populations are average.

3. Comparison to previous season

Host-seeking mosquito activity this week was higher than average due to the staggered emergence of Ae. vexans as a result of previous flooding events. Coquillettidia perturbans populations remain high in many parts of Norfolk County but seem to have slipped off their peaks for each trap site. Ps. feroxpopulations remain high in Canton, with sporadic spikes throughout Norfolk County. Isolated populations of Culex pipiens/restuans remain strong in some parts of the county. Gravid trap activity for Norfolk County was varied and may be a result of scattered rain events disturbing and/or flooding larval habitat of this species. In general, gravid trap collections for Norfolk County were lower than average with only Franklin and Sharon reporting higher than normal activity.

4. Weather Summary

We returned to a wet pattern this week with temperatures near normal to below normal depending on the day. Showery periods on Tuesday and in the predawn hours on Wednesday produced generally between ½ and ¾ of an inch county-wide. A more substantial storm with tropical origins produced widespread 2-3 inches of rain with the highest amounts in the west. While this amount of rain fell short of producing significant flooding, it did raise our river levels enough to cause some potential inundation on the flood plains near the main channels, and the rivers are running well above normal for this time of the year. This rain also left the ground very saturated and primed for any future heavy rainfall events. Monthly rain is well above normal (5-7 inches county-wide) and now most areas have above normal rainfall for the year.

Total weekly rainfall: 2.75 inches (+2.06 in.)
Total Monthly rainfall: 6.21 inches (+3.75 in.)
Total Yearly rainfall: 25.99 inches (+2.25 in.)

5. Number of requests for service

NCMCP received 3,134 calls for service as of 7/24/09. NCMCP received 470 calls for service this week.

6. MCP/Commission response

NCMCP continues to conduct “area wide” ground ULV applications in areas of high calls; where virus has been identified or where light trap/landing count collections dictate additional applications. Due to an increase in demand these ULV activities have been expanded this week. Site visits indicate high levels of host seeking mosquitoes (10+ landings per minute) in many areas. NCMCP is also responding in these areas with increased ULV applications. NCMCP continues treatments to rain basins in high density basin areas such as centers of towns although these activities have been interrupted from time to time due to redeployment of field staff to other ground larvicide activities. As a result of the WNv positive pool collected by DPH in Walpole, DPH has requested that NCMCP set additional traps in the area. NCMCP will deploy additional gravid traps and CDC light traps in select areas of Walpole proximate to the DPH site early next week. NCMCP has coordinated with the Walpole Board of Health relative to control efforts and public notification/ education. Coordination between NCMCP and all 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.

Contact

144 Production Rd, Suite C

Walpole, MA 02081

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