Following Recent Rains, West U Residents Should Prepare For Mosquito Onslaught

July 5, 2010

Rains and flooding from Hurricane Alex likely will lead to significantly increased mosquito activity in many parts of the state, including the West U area, Texas AgriLife Extension Service experts have predicted.

Dr. Mark Johnsen, a medical entomologist with the AgriLife Extension agricultural and environmental safety unite in College Station, said understanding mosquitoes can help in dealing with the pesky insects.

“Excessive moisture and flooding help create optimal conditions in which mosquitoes can breed,” Johnsen said. “And having good information on mosquito behavior and control can help reduce both their nuisance factor and the threat of disease transmission.”

Two waves of mosquito activity typically follow a flooding event, he said.

The first wave occurs five to seven days after the flooding event and consists of “floodwater” mosquitoes, which include salt marsh and pastureland mosquitoes, usually more of an annoyance than a disease threat. The second wave usually comes a few weeks later and consists mainly of “standing-water” mosquito species which breed in stagnating post-flood locations.

“Post-flood mosquito species are those which are the primary vectors of disease,” Johnsen said. “And the southern house mosquito is the most significant of these since it has been identified as the main vector for spreading West Nile virus and St. Louis encephalitis.”

The best way to combat mosquitoes after flooding is by applying the “four Ds” of personal protection – DEET, dusk/dawn, dress and drain, according to Johnsen.

The first D refers to using a mosquito repellent with DEET, picaridin, oil of lemon eucalyptus or IR3535, he said. The second D means restricting activity at dusk and dawn when mosquitoes are most active. The third refers to dressing in loose-fitting, light-colored, long-sleeve shirts or blouses, and long pants. And the fourth D is in reference to draining standing water from bottles, cups, unused plant pots, tires and other receptacles that might provide a mosquito breeding site.

Johnsen added that materials covering the four Ds and other information on mosquitoes and mosquito control are available in English and Spanish and can be downloaded free from two AgriLife Extension websites.

The AgriLife Extension publication, “Potential Mosquito Problems after a Hurricane,” is available for free download at the Agricultural and Environmental Safety website,, as are the other free publications “Mosquito Life Cycle” and “The Best Way to Control Mosquitoes.”

Further information can be found in the AgriLife Extension publication, “Mosquito Problems after a Storm,” available though the AgriLife Extension Bookstore at The publication number for the English-language version is ER-042, and the number for the Spanish-language version is ER-042S.

Additionally, the Texas Department of State Health Services has health-related precautions, including precautions about mosquitoes, for people in areas where heavy rains may occur as a result of Hurricane Alex. These can be found at

Another resource, the “Mosquito Safari” website,, sponsored by AgriLife Extension, the Dallas County Health Department and U.S. Environmental Protection Agency – Region 6 Pesticides Division, is a free interactive site containing scientifically based information on mosquitoes and their control.

“Mosquito Safari was created as an alternative to other Internet sites on the pests that are bogged down by heavily text-oriented pages,” said Dr. Mike Merchant, an AgriLife Extension urban entomologist in Dallas who helped create the site. “It’s a visually appealing and interactive site that helps the user search out and eliminate places where disease-carrying mosquitoes might breed.”

Container-breeding mosquitoes breed in anything that can catch and hold water, including soft drink cans, open grills, watering cans, clogged gutters, wheelbarrows and used tires, Merchant said.

“The core of the Mosquito Safari site is a virtual backyard that you can explore with your computer mouse,” he said. “As you hit hot spots in the backyard, a window pops up and a narrator discusses what appears on the screen and how it relates to mosquito control.”

In addition to showing the most common places for mosquitoes to breed, the site discusses mosquito biology and control methods, including repellents for people and sprays for foliage. It also describes characteristics of six common U.S. mosquito species, including behavior, physical characteristics and breeding sites.

“While the site provides useful information and technical assistance to the public, it may still be necessary for people to contact a pest control professional or employ additional do-it-yourself methods,” he said.

Mosquito spraying in West U occurs weekly between April and October.

InstantNewsWestu Staff

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