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John Fulton

John Fulton
Former County Extension Director

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In The Backyard

Horticulture columns and tips done on a timely basis

Mosquitoes and West Nile Virus

Posted by John Fulton -

With the first confirmed mosquito carrying West Nile Virus (WNV) in Illinois, it's time to examine the disease potential – and what can be done to prevent it. With the extremely wet weather we have had this year, being outside is not very pleasant about dusk. The mosquito numbers are becoming rather large, and WNV is of particular concern again this year. WNV was first isolated in Uganda, Africa. It can harm humans, birds, and other animals. It is transmitted by infected mosquitoes, primarily the northern house mosquito. The mosquito becomes infected after biting wild birds that are the primary host of the virus. The mosquito is actually able to transmit the virus after 10-14 days after biting the infected bird.

The mosquito life cycle has four life stages (egg, larvae, pupa, and adult). The female mosquito lays eggs on water or moist soil. Most of the larvae hatch after 48 hours and the larvae and pupae live in the water. The females need a blood meal before they can lay eggs, so only the females bite. They bite every few days during their adult lives, which may last several weeks.

Preventing mosquitoes is a first step. Homeowners can best accomplish this by eliminating standing water. Tires and old containers are obvious places to start, drill holes in the bottom of recycling containers, clean clogged gutters, don't allow stagnant water in anything such as birdbaths, change landscape slopes to eliminate standing water, and use larvacides in standing water that can't be eliminated. B.t. Israeli is the strain that is effective against mosquito larvae – not the B.t. kurstaki variety commonly used on trees and gardens to kill larvae of moths and butterflies! The mosquitoes have already begun hatching, so treatment time is at hand.

Also protect yourself from bites. Mosquitoes can travel up to three miles from their breeding sites! Make sure that screens and doors are tight, use proper outside lighting such as fluorescent lights, stay indoors at dawn and dusk when mosquitoes are most active, wear long-sleeved shirt and long pants when you must go outside, and use insect repellents properly applied. The Centers for Disease Control is currently recommending DEET, picaridin, and oil of lemon eucalyptus (similar to very low DEET concentrations in repelling mosquitoes). Permethrin for clothing treatment is also available at stores selling outdoor sports and camping supplies. Read and follow all label directions. The DEET percentage affects the length of repelling mosquitoes. For example, a 4.75% DEET lasts about 1.5 hours and 20% lasts about four hours.

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