Why is Aedes aegypti different from the mosquitoes I grew up with?
It bites in the daytime, prefers people, and breeds in tiny containers near homes instead of marshes or washes. It first appeared in the valley around 2017 and has spread to more than 60 ZIP codes. That means the problem is usually in your yard and your neighbors' yards, not out in the desert.
Many mosquito species bite mostly at dusk and dawn, so a person can avoid them by staying in at night. Aedes aegypti does not follow that rule. It bites in broad daylight and rests low in shade, so ankles and wrists are the usual targets.
The first Aedes aegypti found in the valley was in a North Las Vegas ZIP code in May 2017. Since then it has moved across the valley, helped by container habitat that people create without noticing: planters, trays, buckets and pool covers.
What backyard water actually breeds mosquitoes here?
Any container that holds water for about a week can breed Aedes aegypti: plant saucers, drip trays, buried irrigation boxes, bird baths, gutters, tarps, buckets, pool covers and old tires. In a dry city, these small sources matter more than any large body of water.
Drip irrigation and gravel yards mean water often sits where you do not look: in the bottom of a meter box, in a clogged emitter tray or in a tilted pot saucer. A pool cover with a pocket of rainwater after a monsoon storm is another common one. The fix is usually simple, such as dumping, flipping or draining.
Water you cannot dump, such as a decorative fountain or a pond, can be treated with a labeled larvicide. A fountain with a working pump keeps water moving, which helps, but it still needs checking.
- Empty plant saucers and drip trays weekly
- Check irrigation boxes and clean gutters
- Drain pool covers, tarps and buckets after storms
- Scrub bird baths and pet bowls every few days
- Fix slow leaks at spigots and valves
Are Las Vegas mosquitoes a West Nile risk?
Yes, to a small degree. Aedes aegypti has tested positive for West Nile virus in Clark County, and the Southern Nevada Health District runs mosquito surveillance and testing each season. Officials describe the risk of serious illness as small. Preventing bites and removing standing water is the practical response.
West Nile is carried to people by mosquitoes that have fed on infected birds. Most people who are bitten have no symptoms at all, and the chance of serious illness is small. Anyone with a severe headache, high fever or confusion after a bite should see a doctor.
For your own yard, the answer is the same whatever the disease worry: fewer breeding spots, fewer bites. The Health District publishes surveillance information, and the CDC and the Health District are the places to check for current guidance.
What does the monsoon change about mosquito season?
Monsoon storms from early July to mid-September can leave standing water in pool covers, planters, low spots and flood-control channels, and more mosquitoes can follow. The storms are often heavier over the mountains than the valley floor, but a single downpour can refill containers all over a yard.
A wash or a detention basin that is dry for weeks may hold water for a day or two after a big storm. Closer to home, saucers, trays and covers fill in minutes. Walk the yard the morning after a storm and dump what you find.
Hot, dry spells do not end mosquito season either, since irrigation keeps small sources wet. Your technician can tell you which of your water sources keep refilling and which only matter after storms.
