Week 28 – July 9 – 10

2008 Mosquito Report: Week 28

Report based on data collected from traps deployed on Wednesday, July 9, 2008 and retrieved on Thursday, July 10, 2008. Report prepared by John Smith, Chan Suom, M.S., and Nate Boonisar.

1. Current mosquito activity/trend

CDC Light Traps:
Activity levels for CDC traps remained lower this week compared to the average. The most predominant CDC trapped mosquito species was once again Coquillettidia perturbans. Ochlerotatus canadensis and Ochlerotatus excrucians activity has dropped dramatically. The weather has been relatively dry and has impeded mosquito emergence by limiting/eliminating habitat. Coquillettidia perturbans numbers are increasing although still well below the averages in most locations. Culiseta melanura numbers remain low in those traps which collect them.

Gravid Traps:
Mosquito activity in gravid traps has remained relatively steady compared to last year’s figures, although there has been an increase in activity in the towns of Bellingham, Braintree, Canton, Norfolk, Quincy, Randolph, Sharon, Stoughton, and Walpole. Gravid activity is comparably similar to last year’s figures except in the noted towns above. There seems to have been a decline in Culex pipiens/restuans collections in some of the eastern trap locations (Avon, Dedham and Milton) which have shown the highest numbers. It is hard to tell if this is a downward trend or a one week phenomena. Several other trap locations, especially Needham (which has shown previous WNv activity) and Holbrook, showed dramatic spikes in activity. Ocherlotatus japonicus collections remain low.

2. Current Predominant Species

The most predominant CDC trapped mosquitoes were Coquillettidia perturbans followed by Ochlerotatus canadensis. Culex pipiens/restuans is the most abundant species collected in gravid traps.

3. Comparison to previous season

Compared to last season, activity of the predominant species Coquillettidia perturbans in light traps is well below average. Above average collections ofCulex pipiens/restuans have occurred in gravid traps especially in eastern locations of the county although there was a decline in some of the most productive trap locations in the eastern third of the county. Coquillettidia perturbans collections seem late and below normal (in most locations) for this year. Ochlerotatus canadensis numbers are declining fairly rapidly in most cases and remain below their averages. A few Aedes vexans are showing up in some CDC traps no doubt due to recent heavy rain events in the past couple of weeks.

4. Weather Summary

Most of the county received no rainfall during the week; however, a line of thunderstorms associated with a cold front on Wednesday skimmed far northern sections with rainfall maxing out around 0.25 inches in Needham. Somewhat dry conditions continue with 90-day rainfall running 50-75% of normal county wide, except 75-90% of normal in the extreme north (Needham). Temperatures were generally near to slightly above normal, especially mid-week.

Total weekly rainfall: 0.00 inches (-0.59 in.)
Total Monthly rainfall: 1.85 inches (+0.66 in)
Total Yearly rainfall: 23.75 inches (+1.28 in.)

5. Number of requests for service

Year to date NCMCP has received 2,089 calls for service as of 7/12/08. This represents a total of 291 calls for the week. This shows a slight increase in calls from last week. The two highest communities for calls were Foxborough and Weymouth. Last year at this time the calls for service (year to date) were 3,585. Calls for service this year continue to run almost 1,500 less than at this same time last year.

6. MCP/Commission response

In general our response has been to continue ground ULV applications targeting areas of high public demand. NCMCP continues to treat rain basins in highly urban areas where Culex pipiens/restuans activity is highest based on gravid trap collections. Due to a high tide event around the July 4th holiday we assigned crews to larvicide known larval development sites on the salt marshes of Quincy, Milton and Weymouth.


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Walpole, MA 02081

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