Extended cool temperatures have greatly delayed floodwater mosquito development. Although mosquito-biting reports have been minimal from our crews and the public, adult male floodwater mosquitoes (Aedes vexans) have been observed. Typically, male Aedes vexans develop quicker than females preceding them by about 3 days depending on temperatures. It is likely that mosquitoes will become more noticeable by the end of the week and, unfortunately, the Memorial Day holiday if evening temperatures increase. Currently, Aedes vexans has not been implicated as a vector of West Nile Virus to humans. However, this mammal-biting mosquito was found infected with the virus in Illinois even though it is not considered a very competent vector of WNV. More research on this mosquito is needed to determine its role, if any, in the WNV transmission cycle. It is important to understand that just because a mosquito has been found infected with WNV doesn’t necessarily mean it can transmit the virus and infect other hosts.

Larviciding efforts have been directed toward floodwater mosquito control using the insect growth regulator methoprene (a.k.a. Altosid) District-wide. This residual treatment used in mosquito producing water areas will allow us more time to focus on Culex mosquito control which will start to pick up when warmer weather arrives. It is likely, weather permitting, that crews will return to catch basin treatments next week as water temperatures rise in these subterranean Culex production areas. Backyard catch basin treatments have begun in Wheeling, Elk Grove, and Maine Townships and will now be expanded to the remaining 6 Townships in our District.

Light trap counts are averaging in the low single digits below our threshold for adult mosquito spraying in our New Jersey traps. This will most likely change dramatically when warmer weather arrives.

MOSQUITO VIRUS SURVEILLANCE IN ILLINOIS

The Illinois Department of Public Health reports that birds from Hancock, Knox, Stephenson and Tazewell counties have tested negative for West Nile Virus. WNV positive horses have been found in Minnesota, Michigan, South Dakota and Toronto Canada. So far no confirmed human cases have been reported. WNV positive birds have been reported in the Gulf States. Louisiana is reporting WNV infected birds, which is significant with regards to the migratory bird routes along the Mississippi flyway to the Midwest. Current information about WNV can be found on the state’s website www.idph.state.il.us/envhealth/wnv.htm or by calling 217-782-5830.

To date NWMAD has tested (VecTest) 5 Culex mosquito pools from the villages of Des Plaines, Wheeling and Barrington. All mosquito batches were negative for West Nile Virus and St. Louis encephalitis. All samples will be sent to the Illinois Natural History Survey for TaqMan PCR confirmation.

BACKYARD CATCH BASIN TREATMENTS:

NWMAD has already begun treatment of backyard catch basins with the insect growth regulator methoprene (a.k.a. Altosid). The formulation of briquette we place in the basins will provide season long mosquito control as long as the basins are not cleaned out so that the briquette is removed. Rainfall and additional water (i.e. lawn sprinkling) will not reduce the effectiveness of the treatment. Altosid briquettes are not harmful to people or pets. Basins are only treated if they have sumps or pits that collect and hold water for 10 days or longer. For more information on methoprene (Altosid) visit the following website: http://www.epa.gov/pesticides/factsheets/larvicides4mosquitos.htm.

NOTE: Residences that we treat backyard catch basins will receive a yellow door hanger indicating that we performed the treatment as well as additional mosquito prevention suggestions and the District’s phone number for additional information.

DEAD BIRD SURVIELLANCE INFORMATION:

NWMAD has received 22 dead bird reports. Since, the birds were not collected or severely decomposed and not submitted for testing it is not known what they died from. Cities, villages and the public are encouraged to report dead birds to our District’s Dead Bird/Animal reporting web page, which can be accessed at www.nwmadil.com. Knowing this information allows our District to better focus our control efforts. Alternately, dead bird reports can be phoned in to the Cook County Department of Public Health at (708) 492-2035.

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 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 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, birdbaths, flowerpots and barrels that may produce mosquitoes. Neglected swimming pools may produce thousands of mosquitoes. Call the District to report stagnant water areas that remain wet for more than 7 days.

Mike Szyska

Director

DIRECTOR NOTE:

As we enter another potential WNV mosquito season it would be advisable for cities, villages, municipalities, townships, etc. to promote mosquito control-prevention-avoidance activities that residents of the District may employ to help reduce the potential of acquiring mosquito borne diseases. Below are some suggestions you may consider printing in a newsletter or other correspondence that you may send to the residents in your jurisdiction.

Protecting yourself from mosquitoes

The best defense is to eliminate mosquito production places. Here are a few ways to do this:

	Remove or empty water in old tires, tin cans, buckets, drums, bottles or other places where mosquitoes might breed. Be sure to check clogged gutters and flat roofs that may have poor drainage. Make sure cisterns, cesspools; septic tanks, fire barrels, rain barrels and trash containers are covered tightly with a lid or with 16-mesh screen.
	Empty plastic wading pools at least once a week and store indoors when not in use. Unused swimming pools should be covered or drained during the mosquito season. Standing water on pool covers can also produce mosquitoes (Note: If you choose to drain your pool, be sure the hydrostatic relief valve is open in order to keep it from floating out of the ground if the water table rises.).
	Change the water in birdbaths and plant pots or drip trays at least once each week.
	Store boats covered or upside down, or remove rainwater weekly.
	Empty your pet's water bowl daily.
	Level the ground around your home so water can run off and not collect in low spots. Fill in holes or depressions near your home that accumulate water.
	Fill in tree rot holes and hollow stumps that hold water.
	If you have an ornamental water garden, stock it with mosquito-eating fish (e.g., minnows, "mosquito fish," or goldfish). They eat mosquito larvae. You can also add a small fountain; mosquitoes won't lay eggs in rippling water.
	Keep weeds and tall grass cut short; adult mosquitoes look for these shady places to rest during the hot daylight hours.
	Use a flyswatter or household spray to kill mosquitoes, flies or other insects that get into buildings. Spray shrubbery and high weeds to kill adult insects. (Check the insecticide label to make the sure the spray will not damage flowers or ornamental plants.)
	Small impoundments of water can be treated for mosquito larvae with "Bti," a bacterial insecticide. Many hardware stores carry doughnut-shaped Bti briquets (Mosquito Dunks R) for this purpose. Be sure to follow the insecticide label directions exactly.
	Some mosquito control methods are not very effective. Bug zappers are not effective in controlling biting mosquitoes. Various birds and bats will eat mosquitoes, but there is little scientific evidence that this reduces mosquitoes around homes. Mosquitoes make up a small percentage of their diets.
	Avoid places and times when mosquitoes bite. Generally, the peak biting periods occur just before and after sunset and again just before dawn. Each species, however, has its own peak period of biting. Tree-hole and Asian tiger mosquitoes, for example, feed during daylight hours in or near shaded or wooded areas.
	Be sure door and window screens are tight-fitting and in good repair.
	Wear appropriate clothing. Long-sleeved tops and long pants made of tightly woven materials keep mosquitoes away from the skin. Be sure, too, that your clothing is light colored. Keep trouser legs tucked into boots or socks.
	Use mosquito netting when sleeping outdoors or in an unscreened structure and to protect small babies any time.
	Check to see that your mosquito repellent contains DEET (N,N-diethyl-m-toluamide), a chemical commonly found in these products. Generally, repellents with about 25 percent to 35 percent DEET work best for adults; use lower concentrations of 10 percent or less for children between the ages of 2 to 12. Do not use repellents on infants. When outdoors, apply repellent sparingly to exposed skin or clothing, as indicated on the product's label.

Information adapted from the Illinois Department of Public Health.