Mosquito Boom: Three categories of mosquitos you need to be aware of

Between 2002 and 2011, there was one human case of West Nile neuroinvasive disease in Victoria County.

VICTORIA, Texas – Mosquito season is here.

With the amount of rain the Crossroads has experienced, a local expert warns of a mosquito boom.

Forecasters predict more rain heading to the Crossroads area this upcoming week.

Sonja Swiger, Ph.D., Texas A&M Agrilife Extension Service entomologist and associate professor in the College of Agriculture and Life Sciences Department of Entomology shared with 25 News Now the three different categories or waves of mosquitos to be aware of.

The three waves are floodwater mosquitos, container mosquitos and culex mosquitos.

Swiger shared some examples of these waves:

  1. Floodwater mosquitos are the first to emerge right after rain events. Standing water could make their habitat more widespread.
  2. Container mosquitos can be found in anything that might be holding water, tires, buckets and gutters, just to name a few.
  3. Culex mosquitos, those are the ones that carry the West Nile virus.

She also confirmed that between 2002 to 2011 there was one human case of West Nile neuroinvasive disease in Victoria County.

Below are additional statistics of West Nile cases in Victoria County provided by Swiger:

From 2002-2011, there were 3 WNV-positive birds, one horse, one blood donor, and one human case of West Nile neuroinvasive disease (WNND).
2012: one human case of West Nile fever (WNF) and one human WNND case
2015: one WNV-positive horse and three human WNND cases
2016: one WNV-positive horse
No reports of WNV activity in 2013, 2014, 2017, 2018, 2019, or 2020

*Note that we (ZCB) don’t collect denominator data (how many people, animals, or mosquitoes were submitted for testing but were negative), so the lack of cases may only indicate a lack of surveillance/testing.

“They [culex mosquitos] are more prevalent when there isn’t a lot of water, they actually like stagnant water that is higher in organic content,” said Swiger. “So, when it’s raining, we don’t really have that because everything is being washed out … once it stops raining and the water starts to pull and get more concentrated, that’s when we will start to see an increase in the culex species.”

Swiger mentioned the mosquitos that many are experiencing are floodwater mosquitos.

These mosquitos are the first to emerge right after rain events.

Here are more details about the three waves of mosquitos provided by Texas A&M AgriLife Extension Service:

First wave: floodwater mosquitoes
Floodwater mosquitoes are the first to emerge after rain events, Swiger said.

Heavy rains leave the ground saturated and create standing puddles in ditches and low spots in fields and lawns. Floodwater mosquito larvae emerge quickly after water becomes available. Eggs are placed there by females and wait for water, sometimes two to five years before rainfall reaches them depending on the species, Swiger said.

Floodwater mosquitoes are typically larger and are aggressive. These types of mosquitos are often the persistent biters from dawn to dusk, Swiger said.

“The potential for standing water could make their habitat more widespread, which will make them a greater issue for more people than normal,” she said. “Any location that is holding water, even in grassy areas, could be a breeding ground.”

Swiger said females lay more eggs in the moist soil around puddles, and either more larvae emerge, or they will go dormant and wait for water to return. Subsequent rains can wash larvae downstream but can also trigger dormant mosquito eggs.

Second wave: container mosquitoes
Container mosquitoes, which include the Aedes species identified by its black and white body and white striped legs, typically emerge next. Female mosquitoes lay eggs in anything holding water – from tires, buckets and wheelbarrows to gutters, unkept pools and trash cans. They prefer clearer, fresher water, and females are constantly looking for good breeding sites.

Container mosquitoes like Aedes are daytime feeders but can be opportunistic at nighttime when large groups of people gather, Swiger said.

“Anytime after a rain, it is good to make a round on the property to look for anything that might be holding water,” she said. “It just takes a matter of days for these mosquitoes to go from egg to biter, so they can become a problem pretty quickly.”

Third wave: Culex mosquitoes
Culex, a mosquito species that prefers stagnant pools of water with high bacteria content, typically emerge as waters recede and dry summer conditions set in and create breeding sites in low-lying areas. They are the disease carriers that concern the public and health officials, Swiger said.

It is not easy to forecast their emergence because their ideal environment can be washed away by additional rains or dried up by extreme heat and drought, Swiger said. In rural areas, bogs, pooled creek beds or standing water in large containers such as barrels, trash cans or wheelbarrows can make a good habitat for Culex. In the city, similar pools in dried up creeks or other low spots can create breeding sites, but most urban issues occur underground in storm drains where water can sit and stagnate.

“It’s difficult to predict when or where these mosquitoes might become a problem,” she said. “Widespread heavy rain makes it even more difficult to predict.”

How to repel mosquitoes from yourself, children and pets
Swiger said reducing mosquito numbers in your location and the use of spray repellents are a good start when it comes to protecting yourself from bites. Covering exposed skin with long-sleeved shirts and long pants help as well.

Making recommendations for protecting people or locations from mosquitoes can be a tricky proposition, Swiger said. She does not recommend any repellents or mosquito repelling products that are not approved by the Centers for Disease Control and Prevention.

Anecdotal evidence exists that alternatives like essential oils repel mosquitoes, Swiger said. Spatial repellent devices like Thermacell are popular, however some people may balk at the chemical particles the units emit to create a barrier around a person or space.

Plants like citronella, geraniums, lemongrass, lavender, lantana, rosemary and petunias have been shown to repel mosquitoes, but Swiger said the distribution limits effectiveness for protecting a space. The number of plants and the location among other factors would weigh heavily into their effectiveness.

Candles and other smoke-based repellents fall into a similar category as plants, Swiger said.

“Protecting yourself with any spray-on, CDC-approved repellent like DEET, picaridin or lemon eucalyptus oil is my best recommendation anytime you go outside for an extended period,” she said. “Personal protectants are the only certainty against bites.”

Swiger said pets should be removed from areas with mosquito infestations. Small children should not be taken outdoors for long periods if mosquitoes are an issue because they can have adverse reactions to mosquito bites, and spray products should be used sparingly on them, especially babies. There are age restrictions for most repellents; no repellents on babies less than 2 months old and do not use lemon of eucalyptus oil on children 3 and under.

“This time of year, it’s just best to limit their exposure to mosquitoes,” she said.