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Higher Tides Mean An Early Mosquito Season For South Florida

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Emily Michot
/
Miami Herald
During the 2016 Zika outbreak, Miami-Dade Mosquito Control used larvicide to fight mosquitoes.

Surging tides are triggering another nuisance in South Florida: an early mosquito season.

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Miami-Dade County’s mosquito control division received a surge in complaints in April after a high spring tide flooded marshes, hatching swarms of vicious marsh mosquitos. The season usually coincides with spring rains, but mosquito director Bill Petrie said the flooding activated eggs that can sit dormant in swamps and mangrove mud for months.

“You go from having none of these mosquitoes to all of a sudden, bang. You have a massive a emergence and millions of them,” he said.

Unlike others, marsh mosquitoes thrive in saltwater. And they can be aggressive.

“They don’t stalk. They attack,” Petrie said.

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Credit NOAA
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NOAA
Tides peaked between April 7 and 10 during a high spring tide.

He suspects many home-bound residents isolating amid the COVID-19 outbreak may also be behind the rise in complaints as they spend more time in their backyards. Most of the calls are coming from neighborhoods near marshes or mangroves.

Workers have been spraying hard-hit areas using trucks with mounted foggers. The foggers spray a pesticide that kills adult mosquitoes and spray only at night to avoid harming butterflies and bees when they’re least active, he said. They have not been spraying naled, a chemical banned in Europe that drew complaints when it was used to battle Aedes aegypti mosquitoes in South Florida amid the Zika virus outbreak in 2016.

Aedes aegypti mosquitoes live in Florida year-round but tend to surge during the rainy season. They had a small spike in recent weeks, which Petrie suspects is being caused by residents watering more during a spring drought that parched lawns in March and much of April.

For the coming season, Petrie had hoped to test a new method of baiting Aedes aegypti and being developed by the University of Miami. But stay-at-home orders have delayed work since workers need to collect moquitoes to determine where they’re feeding. The method has worked well at battling mosquitoes that carry malaria in Africa, he said.

The coronavirus is also making inspections by mosquito workers harder.

“People are not so happy about us coming in their yards. And we also have to protect our inspectors,” he said.

An ongoing surge in dengue cases in Latin America is causing concern, he said. The World Health Organization reported that the region recorded its highest number of cases ever in 2019 and the number remains high this year. Once countries start to re-open, Petrie worries a surge in travel could increase the presence of the disease in South Florida. Mosquitoes don’t transmit the COVID-19 virus, but patients in Ecuador have been co-infected with the coronavirus and dengue, he said.

“That kind of complicates the situation for public health people and immunologists,” he said. “It doesn't complicate it for us, because all we're trying to do is kill the vector. All we do is kill the Aedes aegypti.”