If you’ve lived in Los Angeles for more than a year or two, chances are you’ve always thought of this as a place with very few, if any, mosquitoes. So you’ve likely been quite surprised this year to find your arms, legs, feet and other body parts covered in itchy red welts after spending time outside. And, no, it’s not your imagination – those really are mosquito bites, and they’re likely from a new (at least in our area) and even more aggressive mosquito – the Invasive Aedes Mosquito.
Just before its regular monthly board meeting, on Wednesday, November 14, the Greater Wilshire Neighborhood council hosted a special Town Hall meeting on Invasive Aedes Mosquitos, with guest speaker Heather Teodoro, from the Greater Los Angeles County Vector Control District.
Teodoro began her presentation by explaining that a “vector” is any organism that can carry disease…and since four of the seven most common kinds of mosquitoes can carry diseases, they are a prime concern of the Vector Control agency.
According to Teodoro, the most effective way to fight insect vectors is to find where they breed and kill them in their larval stage. And with mosquitoes, this is a brief period indeed, since they undergo their complete metamorphosis in just seven days.
But tracking down those brief larvae is an important pursuit, because even though mosquitoes’ breeding period is brief, the rate of the mosquitoes’ reproduction is quite astounding – in fact, just one mosquito can produce up to 8 million more in just 21 days.
The Aedes mosquitoes are different, though, in many ways, from the mosquitoes most of us grew up with, either here or elsewhere. Teodoro said our more traditional mosquitoes tended to be active, and do most of their biting, at dawn and dusk, and they mostly sought out stagnant water to lay their eggs, making them fairly easy to track and eradicate.
The invasive Aedes mosquitoes, however, are active (and will bite) during the day, when more people are out and about. They also lay eggs in a number of different kinds of locations, not just standing water. And they have adapted well to our urban drought conditions. In fact, Teodoro said, some Aedes mosquitoes may lay their eggs on the stems of plants, where they can remain viable for up to two years without any water at all. Also, she said, Aedes mosquitoes are smaller than other mosquitoes, and they lay their eggs individually, so they can get into and breed in smaller spaces than other kinds of mosquitoes. Their small size also means they’re less obvious to humans, and they may bite you before you realize you’re under attack.
Finally, one other difference of Aedes mosquitoes from other types, Teodoro said, is that they don’t fly as far as other mosquitoes do…and, in fact, they may never leave a 150-foot radius, especially in urban areas, which means they tend to concentrate in certain areas once they’ve been introduced there.
Unfortunately, however, humans are often a favorite target for Aedes mosquitoes. According to Teodoro, they are attracted by the smell of carbon dioxide, which humans emit with every exhaled breath, as well as other human odors, like sweat.
When a mosquito bites (and it’s only the females who do so), it injects saliva that contains both an anesthetic and an anti-coagulant, so you may not feel the sting immediately as the parasite sucks your now-free-flowing blood.
One of the most common diseases transmitted by mosquitoes is West Nile Virus, which is commonly carried by (and often fatal to) birds. For up to 80% of humans, however, said Teodoro, West Nile will not lead to a serious illness, and may not even result in any noticeable symptoms. For the other 20% of the population, though, it can cause flu-like symptoms.
The Zika virus is also transmitted by mosquitoes, but although it’s been in the news for the last few years, Teodoro said, there have been no locally acquired cases of Zika in Los Angeles County (most people who contract it have done so in other countries and then traveled to L.A.).
So how can we protect ourselves against invasive Aedes mosquitoes…and how can we keep them from breeding?
First, said Teodoro, you can invite Los Angeles Vector Control to inspect your yard (and the yards of your neighbors) for no charge. The Vector Control employees can help you identify sources of standing water (commonly things like stagnant pools, ponds, and fountains…but also plant saucers, planters, other containers (buckets, pails, etc), old tires, the hollows between raised tree roots, and yes, even plants such as bromeliads, which hold small pools of water in their roots, stems or leaves, and are particularly attractive breeding spots for Aedes mosquitoes).
Also, Teodoro said, one of the most attractive breeding spots for mosquitoes is rain barrels. So if you have a rain barrel, make sure it has a screen with very small openings on the top, to prevent insects from entering. Also, do not open the rain barrel from the top – use the faucet on the bottom to empty water from the barrel.
And what do you do if you do find places where mosquitoes are breeding? Teodoro provided several tips:
- Empty all water-holding containers in your yard
- Empty saucers and turn them upside down so they won’t hold water.
- Get rid of bromeliads or other plants that hold pools of water
- Get mosquito fish to eat the mosquito larvae in stagnant ponds or fountains
- Treat water in ponds, fountains, pools and other places where water stands with Mosquito Dunks or Mosquito Bits, which contain a bacteria that kills mosquito larvae.
And finally, for more information or help, you can always contact Los Angeles County Vector Control, whether you have mosquitoes and want to get rid of them…or whether you want to just prevent them from settling in your yard.