NORTHWEST MOSQUITO ABATEMENT
DISTRICT
147 W. Hintz Rd.
Wheeling, IL. 60090
Phone: (847) 537-2306
Fax: (847) 537-2583
www.nwmadil.com
Mosquito Update
September 27, 2002
PRESENT CONTROL STATUS:
Due to ongoing mosquito
control efforts and cooler temperatures mosquito numbers are very low (single
digit counts) in both our New Jersey light traps and the gravid traps used to
collect Culex mosquitoes. Larval
mosquito control efforts will continue focusing on Culex control in storm water
catch basins and other, typical, stagnant water environments. Insecticide treatments in these Culex
mosquito production areas will be made with 150-day residual insect growth
regulator methoprene (Altosid) and/or Bacillus sphericus.
Due to cooler temperatures all nightly mosquito spraying has been suspended. The cooler temperatures reduce mosquito activity in the evenings decreasing the effectiveness of this control method. This suspension will continue unless mosquito numbers increase in our traps and/or warmer weather returns.
NOTE: Even though the cooler temperatures reduce
mosquito activity residents are still advised to take proper precautions to
avoiding mosquito biting. While less
active, mosquitoes may still bite if their resting areas are disturbed. Also be aware that some mosquitoes may enter
houses attracted to the warmth they provide or with normal in/out house
traffic.
Five hundred fifty one human cases of WNV have been reported in Illinois according to the Illinois Department of Public Health. Cases ranged in age from 3 months to 97 years with an average age of 56. Currently, there have been 29 deaths resulting from WNV. Deaths have occurred in Chicago (6), suburban Cook (14), Clinton (1), DuPage (1), Effingham (2), Fulton (1), Knox (1), Lake (1), Macon (1), Macoupin (1), Madison (1), Moultrie (1), and Sangamon (1) counties.
MOSQUITO VIRUS
SURVEILLANCE IN ILLINOIS:
NWMAD has tested 323 Culex
mosquito batches to date for West Nile Virus (WNV) and St. Louis encephalitis
(SLE) using the VecTest. Seventy-four
mosquito batches have tested positive for WNV.
Currently, no WNV positive mosquitoes have been detected in the District
since 9/15. Mosquitoes testing positive
in the District are posted on the NWMAD website www.nwmadil.com.
A total of 415 horses in 98
counties in Illinois have tested positive for WNV.
DEAD BIRD SURVIELLANCE INFORMATION:
Current information about WNV
dead birds can be found on the state’s website
www.idph.state.il.us/envhealth/wnv.htm
or by calling 217-782-5830.
PHOTOPERIODISM IN MOSQUITOES:
Over time, mosquitoes have
evolved various mechanisms to insure the survival and perpetuation of their
species. Chief among these are various environmental cues like photoperiodism
or diapause resulting from shortened day lengths that change the behavior of
adult mosquitoes (or the hatching of eggs in floodwater mosquitoes) in
preparation for hibernation during the winter months. In simplest terms, it makes no sense for mosquitoes to produce
offspring that are not likely to survive the cold of winter. Therefore, mosquitoes recognize the onset of
fall or winter to prevent wasting resources on propagation. In many cases, when daylight hours become
less than 12 hours an increasing percentage of mosquitoes enter diapause. Temperatures may also induce or modify
diapause in mosquitoes. In some
species, if mosquitoes in the larval stage are exposed to prolonged cooler
temperatures; when they become adults they may not blood feed and lay
eggs. Instead, these mosquitoes will
only feed on carbohydrate sources (i.e. flower nectar) to build up fat reserves
in preparation for hibernation during the winter. Mosquitoes will also produce a natural “antifreeze” in their
blood that prevents tissue damage when exposed to freezing temperatures.
NOTE: From a mosquito control standpoint there is no way to determine exactly when ALL the mosquitoes will enter diapause in preparation for hibernation. Therefore residents are still advised to take mosquito avoidance precautions until temperatures are low enough (generally first hard frost) to prevent all outdoor mosquito activity. Also, be aware, that unusually warm prolonged temperatures may break diapause in some mosquitoes increasing the risk.
Homeowners are now
recommended to dispose of dead birds on their property. The safest method would be to double bag the
dead birds without touching them and dispose of them in their outside garbage
receptacles.
Local health authorities have
also reported higher than average dead birds located near bird feeding areas.
Residents are advised to discontinue wild bird feeding since this activity
increases the likelihood of bringing WNV infected birds into your area and
possibly infecting mosquitoes locally.
Large numbers of birds in such confined areas may also increase the risk
of bird-to-bird transmission of the virus that has been demonstrated in laboratory
studies done by the USGS. It is not
know for certain to what extent bird-to-bird transmission is significant in
nature at this time but we do know that if you feed them you will probably have
to dispose of more dead birds from your property.
REDUCING THE RISK OF
MOSQUITO BITES:
Avoid outdoor activity if
possible from dusk to dawn when the mosquitoes bite the most. If you do go out wear light colored, loose
fitting, protective clothing and insect repellent (always read label warnings
and directions). Make sure mosquitoes
do not enter homes through unscreened or broken doors or windows. Residents are encouraged not to create
mosquito harborage areas. Make sure
tall grassy areas are trimmed and other unnecessary vegetation is cut
back. If plants must be watered do so
in the morning so the vegetation and soil has a chance to dry making it less
attractive to mosquitoes. Empty any
containers holding stagnating water for 7 days or longer like: tire casings, bird baths, flower pots and barrels that may
produce mosquitoes. Neglected swimming pools may produce thousands of
mosquitoes. Call the District to report
large stagnant water areas that remain wet for more than 7 days.
Mike Szyska
Director