Sacramento could see more mosquitoes this spring after onslaught of wet weather

Sacramento residents are warned to be “mosquito aware,” even during years of drought, but this year is shaping up to be a potentially extreme year for the insects in the greater Sacramento area.

After dramatic rainfall this year, the state’s rivers and lakes are full, and our agricultural areas are soaked. Pooled water has accumulated in fields, backyards and roadside ditches, creating  the perfect conditions for mosquitoes — who need standing water to breed — to explode in population size.

But the insects aren’t just pesky — they can carry diseases like West Nile virus, malaria and yellow fever. Local governments track and alert the public when a virus is found in a bird, animal or human.

With a possible increase in mosquito population this spring and summer, CapRadio’s Vicki Gonzalez spoke with Luz Robles, the Public Information Officer for the Sacramento-Yolo Vector Control District, about how residents can help curb an influx of the insect.

This interview has been edited for clarity and length.

Interview Highlights

On the forecasted severity of this year’s mosquito season

It’s going to be a very busy mosquito season just because we’ve had a record [amount of] rain this year. Every year, usually we have a lull in the rain sometime in February and then followed by a warmer spell. But it seems like this year, it never really stopped raining until now, right? So all this rain has definitely left behind a lot of stagnant water and is definitely something we’re concerned about.

So it’s still a little too early to tell what kind of mosquito season it’s going to be, but based on the amount of rainfall, it is likely going to be a busy season because there are lots of areas that do have stagnant water, not only [in] common household sources, but just in general. Roadside ditches, pastures: A lot of areas could potentially become mosquito breeding sources and create a busy season for us ahead.

On how this year’s mosquito population compares to previous years

We have a laboratory that tracks all of the mosquito trends and the abundance … as of now, mosquito populations are on track with what we’ve seen in previous years. I know that a lot of people think that a lot of rain could definitely make it for a lot of mosquitoes, and for sure, it can.

But it’s also important to understand that just because there’s a lot of mosquitoes, that doesn’t necessarily mean that we might have intense virus activity. In years past, when we’ve been in a drought, we have seen intense levels of West Nile Virus activity, even though there was a drought.

So this year, yes, we might see lots of mosquitoes because of the rain and all the stagnant water. But in terms of virus activity, obviously, intense mosquito populations could lead to intense virus activity as well.

But as of now, it’s still a little bit too early to tell. Our laboratory surveillance activities will start at the beginning of May. That’s when we will start tracking West Nile Virus activity in bird populations, and that’s really when the season will really … come to a start.

On how much stagnant water mosquitoes need to start breeding

Even a small amount of water — say in a bucket, a plant source, or a birdbath, a kiddy pool, a dog dish — even that small amount is enough to produce mosquitoes.

We actually have invasive mosquitoes that have started spreading throughout our area, and these mosquitoes only need about a teaspoon of water in order to begin their life cycle. We ask that people, at least once a week, please do their part, look around their yard and dump out any stagnant water and also even scrub down those containers, because some of those invasive mosquitoes, they can lay eggs along the sides of containers.

On how invasive mosquitoes differ from native mosquitoes

We have two species of invasive mosquitoes — Aedes aegypti and Aedes albopictus — that have been in California since 2011, but in our region, we discovered them for the first time in 2019. They’ve been slowly spreading to different areas.

What makes these mosquitoes different is that they’re more aggressive day-biting mosquitoes. Our traditional native mosquitoes bite typically at dawn and dusk. These can bite aggressively all day long. They really prefer to bite people [over animals]. And then also, these mosquitoes can transmit new diseases such as Zika, Dengue [fever] and Chikungunya [virus]. [These are] diseases that are very common in other parts of the world, and not necessarily here in California.

We have not had any locally transmitted diseases here, but we do see those diseases imported from other countries every year … then that increases the possibility that we could also see those diseases locally.