Science
As mosquitoes go year-round in L.A., a promising fix hits a snag
Residents were supposed to get a respite from the ankle-nipping mosquitoes that fueled a recent surge in dengue fever in Los Angeles County.
Typically, the invasive mosquitoes — called Aedes aegypti — essentially disappear from winter until early May in the region.
Instead, complaints to local agencies tasked with controlling the pests spiked recently.
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“We have not seen them go away altogether like they have in previous years,” said Susanne Kluh, general manager for the Greater Los Angeles County Vector Control District.
Their unusual presence adds to the urgency of work going on in a 40-foot shipping container tucked away in Pacoima. It’s about to transform into a bustling nursery for tens of thousands of mosquitoes.
This May, the district is set for the third year in a row to release legions of sterilized male mosquitoes — which don’t bite — into parts of Sunland-Tujunga.
The last two years were promising, with the female population in two treated neighborhoods plunging by an average of more than 80%.
Yet business owners have signaled they’re not willing to pay to expand it.
That’s thrown uncertainty into officials’ goal of eventually bringing the approach to their whole service area, spanning 36 cities and unincorporated communities.
Steve Vetrone, assistant general manager at the Greater L.A. district.
(Ronaldo Bolanos / Los Angeles Times)
“Unfortunately, that’s going to be a rather expensive endeavor,” said Steve Vetrone, an assistant general manager for the district. “I can tell you right now that’s not something that we can do with our current operating budget.”
A need, an ask and a disappointing answer
Aedes aegypti are a new-ish local fixture. Native to Africa, the black-and-white striped mosquitoes were first detected in California in 2013 and landed in L.A. County the following year.
“Despite our best efforts, they’ve been able to just outpace us, and they’re now in every city and community within our district,” and all of Southern California, Vetrone said. In fact, the low-flying, day-biting mosquitoes are present in nearly half of California’s counties, including Shasta in the far north.
Desperate to find a solution, many are trying the so-called sterile insect technique — including vector control districts serving Orange and San Bernardino counties, as well as the San Gabriel Valley — and “we kind of all hope that this is going to be our silver bullet,” Kluh said.
The idea is fairly simple: unleash sterile males so that they far outnumber wild ones — say, 10 to 1 or even 100 to 1. The goal is for the altered males to mate with females, producing eggs that don’t hatch.
Kluh’s district uses X-rays to sterilize males but there are other methods, such as using genetically modified insects or ones infected with bacteria.
Female mosquitoes are fed different types of blood — pig and cow — to see which leads to the most eggs.
(Ronaldo Bolanos / Los Angeles Times)
The technique, while promising, requires time and money.
In California, property owners foot the bill for local mosquito (and other pest) control, with some paying an annual fee called a benefit assessment.
Levying a new fee requires approval from home, apartment and business owners, in accordance with Proposition 218.
To unleash sterile male mosquitoes in a broader swath of the Greater L.A. district, officials are seeking up to $20 a year per single family home. That would be on top of $18.97 that homeowners now pay for the agency’s services.
Last April, the district sent out 50,000 sample ballots to property owners, asking if they’d support the increase.
Only 47% of those returned were in favor.
“Data showed that single family homeowners were pretty supportive, but fewer business owners with larger parcels and potentially higher dues did not see the benefit in the additional expense,” Kluh said in an email.
Business owners might not live in the area, but their vote — if their property spans several acres — is weighted more heavily.
Times readers, commenting on a story from last year about the proposal, responded favorably.
“I hate mosquitos because they love me so much,” one reader said. “I would happily spend $20 to reduce their populations! I probably spend more [than] that on repellent.”
Officials haven’t given up, and plan to send out another round of sample ballots next year.
Kluh already has talking points for businesses in her back pocket: Restaurant owners should have an interest in making outdoor dining more pleasant, while apartment owners could lose revenue if their renters are sickened by an outbreak of Zika, chikungunya or yellow fever — all diseases transmitted by Aedes aegypti, she said.
Making mosquitoes that can’t reproduce
On a recent tour of the Pacoima insectary, Nicolas Tremblay, a senior vector ecologist with the district, whipped out a small container filled with a handful of what looked like vitamins.
But the clear pill cases were filled with about 6,500 mosquito eggs and bovine liver powder.
Nicolas Tremblay, senior vector ecologist, tapes trays to indicate pill capsules filled with mosquito eggs were placed in water.
(Ronaldo Bolanos / Los Angeles Times)
The pills are dropped into trays of water, where the eggs hatch and the larvae feed on the powder. It takes about nine days to go from egg to buzzing adult.
The males are then chauffeured to Garden Grove, where they’re zapped with X-rays. Then they’re driven back and set free the next day.
“It’s crazier around August, September, is when we’ll probably reach our peak production” of up to 72,000 mosquitoes a week, he said. “All these [trays] would be full of water and mosquitoes.”
In 2024, the district launched its pilot, releasing nearly 600,000 sterilized males in two Sunland-Tujunga neighborhoods over about five months.
The population of Aedes aegypti females dropped by an average of 82% compared with a control area.
The stakes became clear that year, when California reported 18 locally acquired dengue cases — a sharp rise from the first-ever cases confirmed the year before.
Last year, the pilot saw similar success, though there was also a natural drop in activity districtwide.
On the recent visit to the insectary, several hundred mosquitoes flew around in white mesh cages, serving as participants in a study to see which blood they prefer — pig or cow.
“We haven’t completed the trials yet, but it seems like they didn’t care,” he said.
One thing scientists already know: Aedes aegypti love biting people.
A highly adaptive foe
The invasive mosquitoes can lay their eggs in tiny amounts of water. A bottle cap or crease in a potato chip bag is fair game.
What’s more, mosquitoes in the Greater L.A. district are resistant to a lot of pesticides.
Now, there might be a new concern. Typically, the invasive mosquitoes go into a type of hibernation every year.
Kluh said it appeared that they may have mutated in a way that allows them to stay active through the winter.
A warming climate has already expanded their season and allowed them to move into formerly inhospitable regions.
Releasing sterilized males involves no pesticides, and also leverages the insect’s biology: Males in lust are adept at finding females.
Many residents are thrilled by the promising tool, but others bristle at the idea of manipulating nature.
“There’s folks that are in favor and then there are folks that are just absolutely opposed because it’s like, ‘You’re playing God,’” Vetrone said.
Science
Pacifica pier cracks, another coastal casualty as seas continue to rise
The Pacifica Municipal Pier was shut down and taped off Thursday after city workers noticed cracks running through the landmark structure and concrete chunks falling into the ocean.
It’s just one of many coastal California structures that have recently crumbled under pressure from a rising and relentless ocean.
Officials from the small, beach city south of San Francisco said the pier was closed due to “cracking, separation, and displacement of the concrete walkway and structural elements.”
It will stay closed while structural engineers asses its safety.
Photos taken by city employees show a wide crack that runs from top to bottom and across the structure as well. Other photos show a large horizontal crack under the foundation of a small restaurant on the pier, the Chit Chat Cafe.
The cafe was also shut down.
This is not the first time the 53-year-old pier has shown signs of stress. In 2021, part of it was shut down after handrails along the edge collapsed. And in 2023, after a series of storms pummeled the Central California coast, damaging parts of the pier, the structure was partially closed for more than year.
Those same storms caused extensive damage in Aptos and Capitola, 70 miles south, where piers and waterfront infrastructure were swept away or damaged.
In 2024, a 150- to 180- foot section of the Santa Cruz wharf was ripped off by powerful waves.
At least 10 of the state’s dozens of coastal public piers were closed for part or all of 2024 due to structural damage sustained in winter storms since 2022. At least five others have longer-term upgrades planned to address structural issues.
“These things are costly to maintain,” said Zach Plopper, senior environmental director at Surfrider. “They are a part of our California coastal culture in many ways, but we’re going to need to reckon with, one, the state that they’re in, and two, the continuous and worsening threats they’re going to experience,”
He said most of the piers were constructed in the early 1900s, and they weren’t built to withstand decades of rough seas, storms and rising sea level.
“With this incoming El Niño, which is forecasted to be significant, and this marine heat wave we’re in the midst of, we’re kind of in uncharted waters as far as what this winter could bring in terms of storms and swells to the California coast, and we’re likely going to see a lot more damage,” he said. “Not just piers, but roads and other coastal infrastructure up and down the state.”
There was no storm in Pacifica earlier this week, so no single event could be blamed for the destruction.
However, a 2025 report from an outside engineering firm, GHD, found that several sections of the pier were in “poor” or “serious” condition, and they recommended closure before anticipated storms or events that could “subject the piles to high winds, swells and large waves.”
The firm found several areas of the pier where concrete was missing and rebar was exposed and corroding.
“The pier has continued to experience high winds and large waves in a harsh marine environment,” the engineers wrote in the report, noting that continuous exposure to seawater or marine spray was “detrimental” to the structure.
A 2023 city report estimated it would cost $19 million to repair.
That same year, a state law was enacted to require local governments along the California coast to plan for sea level rise in the coming decades.
Sea level has risen some 8 inches, on average, along the coast in the past 150 years, Plopper said, and researchers anticipate another foot in the next 25 years.
“We’re going to see profound shifts on our coastline, none that we have ever experienced before, and building static structures on the coast just doesn’t work all that well,” he said. “We’re going to have to make some really hard decisions.”
Science
L.A. region begins the year with the smoggiest first 5 months in a decade
The first five months of 2026 in Southern California have been the smoggiest — with the highest number of unhealtful air days — in more than a decade, according to statewide air monitoring.
So far this year, the South Coast air basin, which includes Los Angeles, Orange, Riverside and San Bernardino counties, has seen 39 days when the concentration of lung-irritating ozone (commonly known as smog) exceeded the federal standard, according to preliminary state air quality data.
That’s even worse than the infamously hot and hazy 2017, when Greater Los Angeles had 36 unhealthful air days by June 4 and ultimately saw 145.
Many of the roughly 18 million people who live in the air basin have been subjected to unhealthful levels of ozone, a highly corrosive gas that triggers asthma attacks and a wide range of respiratory illnesses. This has taken many by surprise since successive days of smog more commonly happen in summer, when heat waves and intense sunlight convert man-made pollution into ozone.
“If we have this many violations by this time, this could be a really awful year for air quality,” said Adrian Martinez, director of Earthjustice’s Right to Zero campaign, an initiative calling for the transition away from fossil fuels. “We’re already the worst place in the country for summertime smog pollution. So it could be one of the worst years in one of the worst places in the country.”
The pollution has been especially severe in valleys. On April 18, an air monitor in Reseda in the San Fernando Valley measured the second highest spike in hourly ozone levels in the last decade.
Greater Los Angeles has seen more high-smog days so far in 2026 than any other year in the past decade.
(Courtesy of South Coast Air Quality Management District)
The South Coast Air Quality Management District says the high ozone levels are due to early heat waves. Officials said they were not aware of any increase in the pollutants — most of them from different kinds of exhaust — that lead to ozone formation.
Local temperatures have been well above normal, climbing into the mid-80s and high 90s between January and April, breaking several daily high temperature records, according to the National Weather Service.
March in particular was the warmest on record in California. Riverside had an unprecedented 13 days of temperatures above 90 degrees, the weather service said.
“It was really that heat wave — conditions we typically see in July or August, we saw them in March,” said Sarah Rees, deputy executive officer of the air district. “That put us ahead of the curve in terms of how much ozone we got.”
Air district officials urged residents to monitor pollution levels on the agency’s website and mobile app, and spend only limited time outdoors when smog levels are high.
“People generally know when there’s a wildfire, because you see the smoke and smell it,” said Scott Epstein, the air district’s manager of planning and rules. “Then, it’s like, I’ve got to take precautions. Ozone, you can’t really tell.”
Southern California has been particularly susceptible to smog formation because of its millions of gas-powered cars releasing tons of tailpipe emissions each day. The region’s sunshine acts as a catalyst for smog formation. Then the mountains trap this pollution over densely populated communities.
For nearly half a century, state and local air regulators have made rules designed to alleviate this pollution, enacting the nation’s first tailpipe emission standards in 1966 and requiring catalytic converters in 1975.
Smog-forming pollution has been dramatically reduced over the last two decades, but the region still does not meet federal air quality standards for ozone.
At an air district meeting Friday in Diamond Bar, the governing board held a moment of silence for William Burke, a former longtime chair. During his tenure, the agency enacted nearly 270 rules that are credited with reducing smog-forming pollution by hundreds of tons per day. Burke, who also founded the Los Angeles Marathon, died in May at 87.
“Those are just emission reductions,” air district Chair Michael Cacciotti said at the Friday meeting. “But what it doesn’t tell you is how many kids, families, seniors were prevented from going to the hospital from an asthma attack, didn’t get cancer or other respiratory problems.”
Several residents from the Inland Empire, which suffers some of the worst smog pollution, expressed their appreciation for the air district’s efforts. But they also stressed the need for more progress.
“I’m old enough to remember growing up in the ‘70s and ‘80s … and not being able to see the mountains for weeks and months at a time,” said Erik Morden, one of several residents who spoke at the meeting.” I know things have improved, and I want to thank all of you for all the hard work that you’re doing. But there’s a lot of invisible stuff that you don’t see, that’s still out there — a lot of particulates in the ozone and chemicals that are causing a lot of problems.”
Martinez, the Earthjustice attorney, said the abnormally early outbreak of smog should be a wake-up call to government regulators that there’s work to be done, including offering more incentives to help residents and businesses transition to zero-emission appliances.
“We shouldn’t over-complicate it. We’ve got a lot of heat, we’ve got a lot of pollution,” Martinez said. “Our contention is, this agency can’t control the weather. But the one thing it can control is the pollution.”
Science
A flesh-eating worm from the 1960s is re-invading the U.S. Are CA cattle at risk?
Federal agricultural inspectors detected a case of New World screwworm larvae — maggots that burrow into the flesh of living animals and sometimes humans — on a 3-week-old calf in south Texas, near the U.S.-Mexico border. Officials anticipated the arrival of screwworm in the United States and say they’re prepared to contain it.
New World screwworm, also known as Cochliomyia hominivorax, is starkly different from the average maggot that feeds on decaying organic matter such as garbage, rotting food or dead animals, said Tom Talbot, veterinarian and member of the California Cattlemen’s Assn.
That’s because a screwworm larva “attacks living flesh,” Talbot said.
On Thursday, the U.S. Department of Agriculture confirmed the detection of New World screwworm in the umbilical area of a bovine in Zavala County, Texas, more than 60 miles from the northern Mexico border.
As of Friday morning, there have been no additional cases of infected animals reported.
Screwworm is endemic in South America and parts of the Caribbean, according to the Centers for Disease Control and Prevention. However, the parasitic fly has been steadily moving north from Central America to Mexico since 2023.
The USDA says it has actively monitored the fly’s movement. Last month, the USDA was aware of more than 200 active screwworm infestation cases in the border states of Nuevo León and Tamaulipas, according to Mexico’s Secretary of Agriculture and Rural Development dashboard. There are currently more than 2,000 active cases throughout Mexico.
It was believed that the New World screwworm would enter the U.S. in 2025, “however, thanks to the hard work across the entire Trump administration and our industry, state, and local partners, we were able to buy time for this moment,” said Dudley Hoskins, undersecretary for Marketing and Regulatory Programs for the USDA, in a statement.
The potential economic impact of New World screwworm on the cattle industry due to import restrictions, reduced productivity and animal loss is substantial, said Sally DeNotta, director of the University of Florida’s Equine Performance Laboratory.
Last year, 175 key agricultural organizations signed a letter urging additional federal funding for screwworm-control measures, emphasizing USDA estimates that a New World screwworm outbreak in the U.S. could cost producers $4.3 billion annually and cause economic losses of more than $10.6 billion across the southern United States.
“While the fly does not survive at temperatures at or below freezing, infected animals could carry the parasite northward and spread infection during the summer months, and the temperate climate of Southern California could certainly support year-round New World screwworm populations,” DeNotta said.
Talbot said from the federal to the local level, everyone in the ranching community has been talking about the arrival of screwworm and how to combat it.
“My expectation is that there will be a minimal number of cases of [New World screwworm] in California,” he said.
That’s because there are several stations on the border in Southern California, he said, that are collecting data, monitoring for any incidents of the parasitic fly and trapping them.
Talbot says he’s confident that the proactive measures on behalf of the federal government will mitigate the screwworm’s reach and therefore not impact the beef supply locally or nationally.
How screwworm infection spreads
Female screwworm flies are attracted to the smell of wounds — that can be as small as a tick bite — and body openings such as the nose, eyes, ears and mouth where they can lay eggs, according to the CDC.
A female screwworm fly can lay 200 to 300 eggs at a time and may lay up to 3,000 eggs during her 10 to 30-day lifespan.
When the eggs hatch into maggots, the maggots eat live tissue, causing a worsening, often painful and foul-smelling wound, according to the CDC.
Screwworm has hit the United States before
There was a screwworm outbreak in the southwestern region of the United States in 1965 that prompted Mexican and U.S. livestock producers to sign a declaration to establish a joint program for the eradication of the screwworm from the states on either side of the Mexico-U.S. border, according to the National Agricultural Library.
By 1966, the United States had eradicated screwworms, but livestock remained vulnerable to reinfestation from screwworms migrating from Mexico.
Eradication was possible through the sterile insect technique, which uses gamma radiation to irradiate screwworm pupae and create sterile male flies.
The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service maintains a screwworm pupae sterilization facility in North America and is currently building a new center in southern Texas.
When produced and released in large numbers, sterile male flies mate with wild female flies, which then lay unfertilized eggs, according to the USDA.
“Since female screwworm flies normally mate only once, the population progressively reduces and is, ultimately, eradicated,” according to USDA officials.
Last year, the Trump administration cut thousands of grants and programs from the U.S. Agency for International Development, which includes U.S.-funded animal disease monitoring projects operated by the United Nations Food and Agriculture Organization, Argi-Pulse Communications reported. Among the slashed programs were some dedicated to monitoring and containing New World screwworm in Central America.
Today, screwworm infestations aren’t a regular occurrence in the U.S., but cases have occurred in travelers returning from areas where the flies are present, according to the CDC.
Can infected animals be treated?
Infected wounds are cleaned and debrided to remove any screwworm larvae, after which the animal is treated with an approved insecticide, DeNotta said.
Last month, the U.S. Food and Drug Administration issued an emergency use authorization for several insecticides known to be effective against screwworm.
There are approved systemic and topical options for a variety of species, including cattle, horses, small ruminants, cats and dogs, DeNotta said.
“Multiple days of treatment are often required, and antibiotics and analgesics may also be administered to treat secondary infection and control pain,” she said.
If left untreated, the tissue destruction caused by flesh-eating larvae can be extensive and severe, often resulting in debilitation and eventual death of the host, DeNotta said.
“Animals that survive may suffer weight loss, poor growth and reduced productivity as a result of pain and discomfort,” she said.
Screwworm can infect humans
Human infection is rare, DeNotta said, but it can happen.
Humans are at risk of being infected by screwworms if they travel to an area where the flies are present, such as South America and the Caribbean, according to the CDC.
CDC officials said your risk of screwworm infection increases when you:
- Spend a lot of time outdoors during the day, especially if sleeping or unable to keep the flies at bay.
- Have any open wounds. A small break in the skin, including from a scratch, insect bite or recent surgery, may attract screwworm flies.
- Have a medical condition that causes bleeding or open sores, such as from skin or sinus cancer, or from treatments that can create breaks in the skin.
- Live, work or spend an extended amount of time with or near, livestock or other warm-blooded animals in areas where screwworm flies are present.
The symptoms humans experience when infected by screwworm
The following are symptoms of screwworm according to the CDC:
- Feeling maggots move or seeing maggots within a skin wound, sore or body opening.
- Painful skin wounds or sores that worsen within a few days.
- Foul-smelling odor from the site of the infestation.
- Bleeding from open sores.
Bacteria can also infect wounds where screwworm maggots are present and may cause an infection that can lead to symptoms like fever or chills.
To treat a screwworm infection, DeNotta said, people undergo the same combination of wound debridement and insecticides used in animals.
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