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San Antonio went from post-freeze fears of drought in early spring to flooding and standing water in late May. And now, with 13-plus inches of rain recorded at the San Antonio International Airport since mid-April, the stage is set for a massive mosquito bloom.

“There’s water sitting in ditches and tree holes and the natural divots in the ground,” said Molly Keck, entomologist and integrated pest management program specialist for San Antonio’s Texas Agrilife Extension office. “And whenever you have water sitting, that breeds mosquitoes.”

To combat mosquitoes and the viruses they can carry, the City of San Antonio uses an approach known as Integrated Pest Management (IPM) to manage mosquitoes and other pests. IPM combines biological, cultural, physical, and chemical tools to identify, manage, and reduce risks from pests as well as the responsible use of insecticides and larvicides, said Joel Lara, supervisor of Vector Control services at the San Antonio Metropolitan Health District. Lara oversees two full-time vector control technicians and 10 licensed noncommercial applicators and is looking to hire nine more applicators.

“It’s very challenging, addressing the mosquito problem,” he said.

The city loads various EPA-approved chemicals into vehicle-mounted sprayers, backpack foggers, and trailers, and deploys them strategically based on the severity of the mosquito problem. The chemical of choice is Permethrin, which is made from chrysanthemums, he said. Workers will switch out chemicals periodically to prevent the mosquitoes from developing a resistance to a particular pesticide.

Residents with severe mosquito problems can contact Vector Control by dialing 311.

“Based on what we’re seeing we’ll send a vector technician out to see where the problems are coming from,” said Lara. “For every resident that wants us to spray for mosquitoes in their neighborhood, there’s another resident that doesn’t want us to.”

People living in unincorporated Bexar County can call a Public Works Service Center at (210)631-0200 to report increased mosquito activity.

Mosquitoes lay their eggs on stagnant water, which serves as a magnet for fertile females. Standing water with organic matter like algae or debris is especially attractive because it provides a food source for the eggs when they hatch after seven to 10 days.

The larvae are called “wigglers” and look like tiny tadpoles, said Keck. Once they morph into pupae, they’re known as “tumblers” because they do somersaults, flipping and turning to escape predators.

Mosquito larvae collect in an inverted position under sitting water. Credit: Courtesy / Texas A&M Agrilife

After a few days, the tiny shrimp-like critters sprout wings, rise to the surface, take flight, and start their quest to annoy us. They dip their proboscis, a matrix of six needlelike mouth parts, into our skin. The needles facilitate blood-sucking and gather a meal that provides protein for the female’s eggs. Both male and female mosquitoes feed on nectar; only females mosquitoes feed on us.

While personal body chemistry determines how attractive someone is to mosquitoes, rainy weather and overcast skies have created a perfect storm for mosquito reproduction. Even people who generally escape serving as mosquito prey are falling victim to their presence.

One Twitter user identified as andy villanueva posted that for two and half years, he’s managed to escape mosquito bites. “Head to San Antonio to visit family and it was an all day buffet on my legs,” he tweeted. Another Twitter user posted: “I think all the mosquitoes from Rockport hitched a ride back to San Antonio in my truck.”

In a recent post on the Insects in the City website, entomologist Sonja Swiger, an associate professor in the College of Agriculture and Life Sciences Department of Entomology at Texas A&M-Stephenville, divided mosquitoes into three categories: floodwater, container, and stagnant. They typically emerge in the order related to the breeding environment they prefer.

First, the floodwater mosquitoes emerge, immediately following rain events. Large and black, they are persistent, fierce biters.

Then come the container mosquitoes, the Aides species. These are identified by their black and white bodies and white-striped legs. They can carry the Zika virus.

Culex mosquitoes, a species that prefers stagnant pools with high bacteria content, emerge as waters recede and the dry summer sets in, according to Swiger. This species can carry Zika and West Nile viruses.

Lara encourages people to eliminate standing water in bird baths, saucers, dog bowls, rain barrels, and elsewhere. Residents also can buy mosquito dunks at retail stores, which can be placed in standing water to prevent mosquito development.

A graphic highlights common breeding grounds for mosquitoes in the typical residential yard. Credit: Courtesy / Texas A&M Agrilife

Metro Health’s main objective in keeping the insects under control is to prevent the spread of Zika and West Nile viruses, both of which are transmitted by mosquitoes.

“That’s why we always preach for the public to eliminate stagnant water,” said Lara.

No local cases of either virus have been reported this year.

Monika Maeckle

San Antonio Report co-founder Monika Maeckle writes about pollinators, native plants, and the ecosystems that sustain them at the Texas Butterfly Ranch website. She is also the founder and director of...