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El Niño Rain Could Bring Mosquitoes, Other Pests

The El Niño weather system could bring more than heavy rain in the coming months. According to the National Oceanic and Atmospheric Administration (NOAA), the Southern United States from California to the Carolinas and up parts of the East Coast will experience wetter than average conditions during the fall and winter as a result of El Niño.

Orkin warns that as long as temperatures stay above freezing in regions where there is above average precipitation, the weather system could also bring an atypical pest season with more mosquitoes, ants, rodents, flies, termites and other occasional invaders.

“Mosquitoes thrive in wet and warm weather,” says Entomologist and Orkin technical Services Director Ron Harrison, Ph.D. “Usually October and November are drier, cooler months causing the mosquito population to decline, but this year could be an exception,” he says, adding that other pests can become a nuisance when displaced by flooding.

El Niño 2006-07 was relatively weak, according to The Weather Channel, but provided some of the driest winter weather ever recorded in parts of California. However, the record-setting 1997-98 El Niño was the warmest and wettest in 104 years and included flooding in the southeast and California. A comparison by the National Center for Atmospheric Research shows revealing similarities between this year’s sea surface temperatures and those in 1997-98, and NOAA confirms that an already strong El Niño will continue into – and likely peak – during winter 2015-16.

Pests Impacted by Flooding:

  • Mosquitoes need only a few inches of standing water to breed and temperatures above freezing to thrive.

  • Ants may be forced to higher, drier ground in the corners and crevices of a home.

  • Fire ants will hook together to form floating rafts and wait out a flood until they can re-establish.

  • Rodents that are forced indoors by flooding may carry diseases with them.

  • Flies feed on garbage, and their population can increase if trash and filth are allowed to collect after a storm.

  • Occasional invaders like centipedes, millipedes, earwigs and roly-polies can slip in under doors when the water table starts to rise.

  • Termites can more easily damage a home if flooding washes away termite-treated soil, leaving a home’s foundation unprotected.

Orkin advises families to continue taking precautions to help prevent pest problems in the event of heavy rain that leaves behind standing water:

  • Empty any standing water from bird baths, flower planters and toys and playground equipment outside the home to help prevent mosquitoes from breeding.

  • Clean gutters and downspouts regularly or cover them with mesh to help prevent leaves and debris from collecting and holding water.

  • Make sure screens around the home, both on windows and doors, fit tightly and have no holes to help keep mosquitoes out of the house.

  • Apply an EPA-registered insect repellent before heading outside.

  • Wear long sleeves and pants outside from dawn to dusk, which is prime time for most mosquito activity.

For more information about preventing pests during a storm, visit

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