Yikes! Ike-related flooding likely to cause mosquito population explosion

Recent flooding, including flooding from storm surge and rains due to Hurricane Ike, likely will lead to significantly increased mosquito activity in many parts of the state, said a Texas AgriLife Extension Service expert.

“Flooding in many parts of the state has created optimal conditions for mosquitoes to breed, making these areas a regular hotbed of mosquito activity,” said Dr. Mark Johnsen, a medical entomologist with the AgriLife Extension department of agricultural and environmental safety.

Johnsen said along with the rise in mosquito activity comes an increased need to understand more about mosquito behavior to ensure better control.

“Having the right information about mosquito behavior and proper control options can help reduce both the nuisance factor and possible threat of disease transmitted by mosquitoes,” he said.

Johnsen noted that two waves of mosquito activity typically follow a flooding event.

“The first wave of mosquitoes are flood-water mosquitoes, including salt marsh and pastureland mosquitoes, which are usually more an annoyance than a disease threat,” he said. “The second wave, which usually comes a few weeks later, consists mainly of standing-water mosquitoes which breed in stagnating post-flood water. These mosquito species have the primary vectors of disease.”

The southern house mosquito is the most significant of the standing-water mosquitoes because it has been identified as the main vector for spreading West Nile virus and St. Louis encephalitis, he said.

“Currently, we are working to support the efforts of Texas Department of State Health Services by doing mosquito surveillance and getting mosquito population numbers to help them determine what type of mosquito control measures need to be implemented,” he said. “But there also are measures individuals can take to help protect themselves and their families.”

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

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 how to dress. Johnsen suggests dressing in loose-fitting, light-colored, long-sleeve shirts or blouses and long pants.

The final D refers to draining bottles, cups, unused plant pots, tires and other items that might provide a breeding ground for mosquitoes.

“You should drain, clean or cover all containers that can hold water for more than three days,” he said.

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 Web sites.

“AgriLife Extension offices in more than 105 flood-affected counties in the Panhandle, as well as Gulf Coast and inland areas of eastern and central Texas affected by Hurricane Ike, have received supplemental materials on mosquito behavior and control,” he said. “This information is usually available through the agricultural and natural resources agents, and family and consumer sciences agents and associated personnel.”

Johnsen said the publication, “Potential Mosquito Problems after a Hurricane,” is available for free download at the Agricultural and Environmental Safety Web site. Other free publications available from this site are “Mosquito Life Cycle” and “The Best Way to Control Mosquitoes.”

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

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