HARLINGEN — Not to be a buzzkill, but the Valley’s mosquito problem is intensifying.
Experts at Texas A&M University say this weekend kicked off peak mosquito season here, as the fallout from heavy rains almost three weeks ago brings wave after wave of hatchling blood-suckers into the world, primed by instinct and inclination to find us and feed.
There are a couple hundred mosquito species that call the Valley home, but not all the females bite (it’s always females, which need a blood meal before laying eggs). Some species feed on animals exclusively, and others on animals and humans.
“Our main concern will be the ones that are vectors of arboviruses, like Zika and dengue, chikungunya for example,” said Ismael E. Badillo-Vargas, an assistant professor of insect vector biology with Texas A&M AgriLife Research in Weslaco.
Danger from above
The two species to worry about, unfortunately, are widespread across the Rio Grande Valley and are as at home in your backyard as the rest of the family.
“Like Aedes aegypti, and the other species that we have here that is related, Aedes albopictus,” Badillo-Vargas said. “Those two, after rain events like this, they will go up in numbers and those are the ones we should be more concerned with because of their ability to transmit pathogens that cause diseases in humans.”
The skinny on these two mosquito species is they appear similar — small-sized black mosquitoes with white stripes on their legs. Albopictus also has white stripes on its body, thus earning its nickname Asian tiger mosquito.
“Predominantly, albopictus prefers to bite at dawn and dusk, but if you have high numbers like what is expected after these rains, they could bite at any time because they are really looking for food,” Badillo-Vargas said. “Albopictus is outside, seeking blood, at dawn and dusk. But definitely with people being outside and outdoors, they can bite at any time.”
Aedes aegypti is adept at breeding in the tiniest thimble of water in containers in urban backyards.
“Those bite at any time during the day,” Badillo-Vargas said. “They are not so much specialized to the degree that aedes albopictus is to bite at dawn and dusk. That one could really be at any time seeking a blood meal.”
Aedes aegypti can transmit Zika, dengue and chikungunya viruses. Aedes albopictus can transmit Zika, dengue, chikungunya and dog heartworm.
It’s nice outside
The subtropical climate of the Valley, where temperatures rarely punch below freezing in a given year, makes mosquitoes a constant issue.
Josh Ramirez is environmental health director for the City of Harlingen, and says without a significant cold season the Valley is unlike Dallas, Houston, Austin or even San Antonio. In all of those places, mosquito control pauses for at least a few weeks each winter.
“Mosquitoes don’t really take a break for us in South Texas,” he said. “Austin shuts down the lab during the winter time because there’s no mosquito surveillance. I’ve worked from McAllen to Brownsville and we do have mosquitoes pretty much all the time.”
Ramirez said even when we are locked in drought conditions, like we were prior to the heavy rains last month, we still have mosquito problems.
“Understand that humidity creates a huge amount of dew and humid condensation,” Ramirez said. “You walk in any grass early in the morning, it’s wet, the floors are wet — it’s humidity.
“That little water, once it accumulates for the first few nights in a little container, that breeds mosquitoes. And people are like, ‘We’re in a drought, how can that be?’ Well you still have a lot of humidity in the air … so we have to spray and be proactive all the time.”
The challenge now
Ramirez said the city normally sprays to kill adult mosquitoes, called adulticide, on average twice a month during usual weather.
But city officials saw the forecast last month, with its prediction of heavy rainfall, and began spraying for mosquitoes even before the rain began falling in sheets. In all, Harlingen received 16.75 inches of rain in 96 hours.
“In similar years of experience in doing this, we’re ahead of the game where we minimize the amount of mosquitoes that would be hatching right now,” he said. “It would have been a lot worse.”
City workers have on multiple occasions sprayed clouds of insecticide around the city to tamp down the numbers of mosquitoes since the deluge hit.
“We still have some, we’re not denying that,” Ramirez added. “I can spray the City of Harlingen very well but we have adjacent communities that are not spraying, we have rural areas where they’re not able to spray because they’re still under water.”
When the winds shift, hungry mosquitoes can ride the breeze from miles away and drift into the city.
City welcomes help
Local officials also have been trying to kill young mosquitoes before they hatch, using larvicide. Donut-shaped granules are tossed in pools of standing water, and the poison kills the mosquitoes at that point in their life cycle.
“We want to kill it at that stage, but the amount of water we received … we understand we can’t get to everything,” Ramirez said.
Which means the city needs help, because adult mosquitoes are cagey about avoiding a cloud of bug spray.
“Mosquitoes are smart, they go hide,” Ramirez said. “So normally when there’s brushy areas, thick brush, thick grass, they go hide.
“You can help us by mowing your grass, keeping it nice and clean, control the brush area right now, trim your trees as well to control the amount of brush we have, and then of course do an inspection of your property, get rid of any standing water or any containers that are holding water,” he added.
Standing water can come in all shapes and sizes of container. In fact, Ramirez said, one of his biggest headaches is chain-link fencing around a property.
“A lot of times I ask people to cap their fence posts,” he said. “We have a lot of chain-link fence around South Texas and some of those posts are not capped. Inside, the water goes in there and starts accumulating, and mosquitoes are smart, they go lay their eggs in there.”
Ramirez said everybody, especially kids preparing for evening baseball games or riding bikes, needs to spray themselves down with mosquito repellent before going outside.
“Our citizens need to help us with that, and we really stress for them to help us, and help themselves as well,” he said. “We’ll do our part, we’re monitoring on a daily basis.”
• Identify and empty all standing water, including bottles, cans and containers
• Turn over wheelbarrows
• Refresh water in birdbaths and animal water bowls
• Dispose of tires and debris
• Keep grass mowed
• Use DEET mosquito repellent when outdoors