Notice a lot more mosquitoes? They’re back.

Mosquito we’ve known for years is the Culex mosquito. Still here but easier to control by getting rid of standing or stagnant water. Besides Culex there are new arrivals harder to control that cause more problems. Aedes aegypti seems the worst because it’s kind of a super-villain with special powers but also weaknesses. A huge problem but one that can be helped by doing just a few things. Unfortunately – solutions aren’t being well communicated. This may help.


  • Doesn’t need to lay eggs in water. This is the game-changer. Eggs last up to 5 years and hatch whenever there’s water and become adults 5 – 8 days later in places you never expected: rain gutters, underground landscape drains, garden plants holding water like bromeliads and agave, trashcans, toys left outside, plant saucers and even a single bottle cap. Standard mosquito-fighting strategy of just finding and dumping water doesn’t solve the problem. You need to do something anywhere there may be water that doesn’t evaporate quickly.
  • They’re active during the day and night so no time to avoid them.
  • They live outside and inside, lay eggs in flower vases, toilet bowls, sink and shower drains especially in bathrooms that aren’t always used. Anywhere there’s water.
  • Also called ankle-biters, they fly fast and take quick bites so they’re hard to swat.
  • A weakness? Culex mosquitoes can fly several miles. Aedes aegypti fly only about 150 yards from where they hatched during their entire lifetime.

Enjoying the outside is a major benefit of living in Southern California and we may be losing that because of Aedes aegypti. Predictions are that unless we do something about these mosquitoes, living in Southern California may feel like living in Florida where entire backyards are protected by giant plastic bubbles. Kind of a nightmare for most Californians. These mosquitoes also carry serious diseases. Something else we don’t need right now.

There’s information about Aedes aegypti at Orange County Mosquito and Vector Control District’s website and Greater Los Angeles County Vector Control District’s website. This article won’t duplicate that information, but will focus on letting you know what they don’t tell you. Apparently because vector control districts are government agencies, there are regulations that discourage them from recommending or warning about products or even active ingredients in products. They give good advice about various products when requested but don’t seem to volunteer. Here’s what I know.

  • Source reduction – Getting rid of non-useful things where water accumulates, and dumping out water from things you need, are every vector control district’s main focus. There are places where you can’t always do that: small fountains, rain gutters that don’t drain completely, underground landscape drains and plants that hold water like bromeliads and some agave.
  • Larvacides – For outside ponds you can get mosquitofish. For those other places, there are larvacides (materials that kill mosquito larva or keep them from turning into adults). Both Orange County and Los Angeles Vector Control Districts mention several options on their websites but don’t fully explain the dangers and benefits of each. Seems they should.
  • For example, Bacillus thuringiensis israelensis (Bti) is as close to a silver bullet for killing mosquitoes that seems to exist. It’s a naturally occurring soil bacterium that only kills mosquitoes and a few flies but is harmless to other insects, birds, animals and humans. For whatever reason neither vector control district’s written info tells you this. More details about Bti available here.
  • It’s readily available in “dunk” or “bit” form, and available to licensed contractors and maybe online in liquid form, which for some applications is better. There are also time-release briquets containing Bti that supposedly last for several months, but don’t seem available in California. Bti dunks and bits need replacement every 30 days, so a time-release briquet would be ideal for places like rain gutters to help keep them mosquito-free. Seems these products should be available locally but they’re not. Something maybe our elected representatives could help with?
  • Bacillus sphaericus (B.s.) is another naturally occurring soil bacterium safe for everything except mosquitoes and usually used in combination with Bti.
  • Spinosad is another naturally occurring soil bacterium but is also harmful to many types of insects including bees. Not sure why vector control districts don’t warn people about this?
  • Methoprene is a mosquito juvenile hormone. It doesn’t kill mosquito larva but supposedly just keeps them from developing into adults. Also on vector control recommended lists (but not on mine). The main concern is that you can’t really see if it’s working. Easier to check the water to see if anything’s wiggling than to see larva and just hope they don’t turn into adults.
  • Adulticides – What we usually think of as pesticides and are used to kill adult mosquitoes. They also kill almost every other type of insect they come in contact with. They kill mosquitoes but only in a limited area and for a short time period. Vector control agencies use as a last resort with aerial spraying or ground based fogging when there’s a mosquito borne disease outbreak. Usually done at night to avoid day-flying insects like bees, they still cause harm to other insects, but sometimes that’s impossible to avoid.
  • Mosquito Traps are available for inside and outside use, and some claim to cover up to a full acre. I can’t vouch for their effectiveness, but at least the inside traps from this company seem to work.
  • New technology and research offer additional options. I can’t personally vouch for the effectiveness of this system and it’s not inexpensive, but the animated video explaining how it works is definitely worth watching.

Hopefully you have at least 5 takeaways:

  1. Research and learn more about the Aedes aegypti mosquito. Huge problem even though most people have never heard about them.
  2. Learn more about products containing Bacillus thuringiensis israelensis (Bti) especially for places like rain gutters. Keep your rain gutters as clean as possible and check them after it rains. After foggy mornings there’s more water coming from condensation than you expect. Vector control agencies talk about single water bottle caps causing problems, but they don’t focus much on rain gutters. Check for yourself.
  3. Work with your immediate neighbors to reduce mosquito breeding locations and help educate them about Bti. Maybe even check their rain gutters if they can’t. If you’re being bitten by Aedes aegypti mosquitoes, they’re either coming from where you live or from your neighbors. You can actually help solve your own mosquito problem.
  4. Push your local vector control agency to do more to help. They are the first to admit they can’t fix this problem without help from residents, but people need more information, more help and more tools to work with.
  5. Also push local elected representatives to get vector control agencies more resources, and also to help make more products available as long as they’re safe and environmentally friendly. My understanding is that most retail garden products started out as commercial agricultural products, and then only became generally available if they had the potential to earn big profits. Vector control agencies aren’t responsible for finding and vetting products for the public but it seems more government involvement would help.

Les Hall is a resident of Santa Ana and retired corporate attorney. 

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