Aggressive, invasive mosquitoes are in San Diego and only you can stop them


SAN DIEGO — A variety of aggressive mosquitoes are in the midst of another successful season biting San Diegans and driving pest control specialists to their wits’ end.

The invasive Aedes mosquitoes — which come in varieties boasting nicknames like “Yellow Fever,” “Asian Tiger” and “Australian Backyard” mosquito — first showed up in San Diego back in 2014. They’ve been driving experts like Chris Conlan, the county’s supervising vector ecologist, crazy ever since.

As Conlan explains it, the Aedes insects have adapted into “urban, suburban” mosquitoes, swapping the rainforest floor puddles and jungle plants of their native habitat for small pools of water in neighborhood backyards, like buckets and plant saucers.

There they breed prolifically. In a pool of water the size of a soda can, they can produce maybe 100 offspring in a week, according to Conlan. Give them a 5-gallon bucket or a kiddie pool and they’ll produce thousands in that span.

This map shows the areas where Aedes mosquitoes have been reported so far in 2021. Aedes aegypti, represented in orange, are by far the most common in San Diego over recent years. Conlan says that so far, this year’s reports are about on par with past seasons. (Photo: County of San Diego)

Once they’ve moved in, you won’t like them. The small, black mosquitoes, which sport white stripes on their legs and back, bite particularly aggressively. They like to strike during the day, especially around legs and ankles, and they specifically prefer human blood to that of birds or other mammals. They bite repeatedly, too, getting their fill of blood in a process that will leave you with several itchy welts.

As adaptable as they are, the mosquitoes are content even if they get inside your home, hanging out under tables or couches so they can “wait for an opportunity to zip out and getcha,” as Conlan puts it.

They’re a hearty bunch, too.

“These darn mosquitoes have extended our mosquito season,” Conlan told FOX 5. While the season would typically peak and then tail off toward the end of summer, the Aedes varieties will keep biting until the weather cools down enough. In ever-pleasant San Diego, that can last through November and even into December.

Further befuddling vector control, the mosquitoes’ preference for small water sources makes some of the county’s tried and true control methods ineffective.

“All these normal things we would do … really don’t work for these guys,” Conlan said. Unlike the rivers, streams, ponds and waterways the county targets with regular larvicide drops, a backyard bucket or clogged storm drain escapes the watchful eye.

“It’s not something we can drive by and spray and fix everything,” Conlan said. “It really is incumbent upon our citizens here in San Diego to do whatever they can.”

So what can you do? “The key is that source removal,” the ecologist says.

Start with obvious things: Empty out kiddie pools and half-empty buckets around your property, dump out the dirty water in that saucer under your backyard planter and put a screen on your rain barrels. Consider a screen over other areas too, like your yard drains, which often house tantalizing pools of water just below the surface. Conlan says any cover with holes the size of a window screen or smaller will do.

If you have a bird bath, fountain or pond, try mosquitofish. The county makes them available for free, and they’ll swim around your small bodies of water hoovering up larvae before they can hatch.

The county has a prevention checklist that goes into further detail.

Mosquito prevention tips from local experts. (Photo: County of San Diego)

A little piece of extra motivation for you and your neighbors: The mosquitoes typically only travel as far as 300 feet from where they’re born, settling down and hunting away in a familiar stomping ground. That means when communities take steps to run the Aedes mosquitoes out of town, they’re unlikely to come back that season.

“It will have an amazing impact,” Conlan said.

And a final piece of heartening news from the ecologist: While the mosquitoes have been known to carry viruses such as Zika, dengue and yellow fever, there have been no recent recorded cases of those illnesses transmitted in California. If the public can keep their populations from swelling further, Conlan says that’s likely to remain the case.

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