West Nile virus (WNV), which is carried by mosquitoes and can be transmitted to humans, has become a common summer time threat in northern Illinois. Its incidence in Illinois has again increased now late in the summer. To help reduce the potential population, try to reduce breeding sites around the home. "Since mosquitoes that carry west nile virus do not travel far from their hatching site, it can be helpful to eliminate such egg-laying sites in your own backyard," says John Church, University of Illinois Extension Educator, Natural Resources, Rockford. They often only travel within one-half mile of their hatching site, so individuals can often help their situation by acting on their own property.

Entomologists at the University of Illinois and Purdue indicate that there are several points to remember about controlling and living with high mosquito populations. The entire life cycle of a mosquito can be completed in about seven to ten days. Anything that interrupts the cycle, such as reducing water availability, before it can be completed is helpful.

There are several varieties of mosquitoes in Illinois. Not all of them carry WNV. The Northern House mosquito, which carries WNV, lays eggs in standing water in places such as ditches, catch basins and other locations, such as water filled containers. Recent research information from the Illinois Department of Public Health indicates that as much as 70% of the breeding sites for the Northern House mosquito are in stormwater catch basins. Other attractive breeding sites in urbanizing areas include construction site tracks and ruts or new basement foundations that hold water. Standing water with organic matter, such as clogged roof gutters, often provide good breeding sites. Persons should eliminate any unnecessary water holding areas and containers, such as old tires. Sites such as wading pools, birdbaths, or pet watering dishes should be cleaned and freshened with new water often. Reducing the incidence of these problem sites will help reduce egg-laying and hatch. Cutting tall grass and weeds can help reduce populations near the home, since it is a favorite hiding place during the day.

Floodwater mosquitoes, which is one of the most common nuisance mosquitoes, does not carry WNV. Their eggs are laid in muddy, temporary pool areas and hatch when flooded by rain or runoff water. Young mosquitoes live as larvae in water, but they are rarely found in deep water such as lakes or in flowing streams or rivers. Shallow, ponded areas are the most preferred sites. However, not all wet areas cause buildups in populations, since wetlands with a balanced diversity of wildlife can actually confine the mosquito population in that area and use it as a food source.

For individuals, remember that dark colored clothing tends to attract mosquitoes. They are often hungriest and most active at dusk and dawn, so less outside activity at that time can reduce biting. The peak biting time for the northern house mosquito is about 8:00 pm to midnight. Keep pets inside during those high feeding times and out of tall grassy areas, since they can also be bitten. Apply insect repellents to exposed skin when going outside and wear long-sleeved shirts and long pants.

Source: John Church, Extension Educator, Natural Resources Management, churchj@uiuc.edu

August 28, 2006