Extreme Weather and Mosquitoes: Challenges and Solutions

Extreme weather events are on the rise in the United States. The National Centers for Environmental Information (NCEI) cited 2023 as an “historic” year for extreme weather, with a record high 28 weather and climate disasters responsible for at least one billion dollars in damages each. That record could be broken in 2024, with the NCEI confirming 15 “billion-dollar” weather and climate disasters through the first week of July. Adding to the economic impact and public safety threat posed by these weather events is the significant strain they put on public mosquito control professionals.

Extreme weather events like droughts, floods, hurricanes, and tornadoes create ideal breeding grounds for mosquitoes. The aftermath of these events can also create unique challenges for mosquito abatement districts attempting to conduct control efforts.

According to Samer Elkashef, Ph.D. and Central Life Sciences sales manager for the western region of the US, the past few years have been particularly challenging.

“We've had flooding, we've had droughts, we had fires and all of that can impact mosquito breeding and control,” said Elkashef. “The droughts in California lasted for years before we transitioned to this atmospheric river era. That was hard because there were not a lot of water sources, which you would think might make things easier, however, they might be harder to find, forcing mosquitoes to localize with birds and increase West Nile virus transmission.”

Elkashef added that atmospheric rivers can also suddenly create large sources of water in regions that are not accustomed to them and may not be prepared to address the mosquito threat they pose. Another often overlooked threat for mosquito control, according to Elkashef, is the higher occurrence of wildfires.

“When you think about fires, you assume there shouldn't be any mosquito issues because you're burning everything and drying everything up,” said Elkashef. “But what ends up happening is you have access issues. You're not able to get to areas where there might be mosquito breeding because the terrain has been devastated.”

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Like the challenge that wildfires present, tornadoes in the Midwest and southeast can leave a path of destruction that makes control efforts extremely difficult, according to Jeromy Baumbach, ACE and mid-central regional sales manager for Central Life Sciences. He added that tornadoes can further complicate control efforts by bringing in mosquitoes and other insects from different areas that are new to the region impacted by the storm.

The Midwest has also been faced with extreme levels of flooding, impacting parts of Nebraska, Iowa, Minnesota, South Dakota and beyond. According to the organization Climate Central, the Midwest has seen its number of extreme precipitation days rise by 45% since the 1950s.

“Anywhere that has stagnant and standing water for seven to 10 days, especially after a flood, all those pockets are just breeding sites for mosquitoes,” said Baumbach. “But the thing is, most of these mosquitoes will actually deposit their eggs on the banks of the dry land. It is amazing because mosquitoes are smarter than you realize, because you may not think that water will rise up to that area, but it has.”

Baumbach said the flooding has led to huge explosions in populations of species such as the Culex pipiens, and Culex tarsalis. His best advice to regions preparing for flooding is to follow an integrated mosquito management program by removing vegetation and debris from ditches, draining or discarding anything that may collect water and filling in low spots in the ground.

Mike Riles, Central Life Sciences sales manager for the southeast region, has seen an increase in thunderstorms, hurricanes and tornadoes throughout the area that can all create ideal conditions for mosquitoes.

“When we think about hurricanes and tornadoes and the destruction they cause, they actually create new environments for mosquitoes to breed and lay eggs,” said Riles. “It takes a long time to remediate the destruction of property in commercial and residential zones, and then you have more rain events coming into those areas before they're cleared out. That causes mosquito issues with your domestic mosquitoes like Culex quinquefasciatus, Culex pipiens, Aedes albopictus and Aedes aegypti that proliferate in areas impacted by destruction, in both standing water and containers.”

Riles added that the rain deposits from these types of storms create specific challenges with floodwater mosquitoes in the genus Psorophora and Aedes.

“These mosquitoes generally lay their eggs in the muck on the fringe of receding water pools throughout the region,” said Riles. “When those pools fill back up with water, those eggs hatch. When you have these crazy hurricane events that are depositing water all over the place, this gives a great opportunity for these mosquitoes to emerge in mass amounts. I'm talking about millions of mosquitoes per acre.”

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With the potential for extreme weather events to bring about such surges in mosquito populations, Riles, Baumbach and Elkashef all agree that having a carefully thought-out strategy in place beforehand is the best approach for dealing with the unpredictable nature of the weather. This includes being properly stocked with the right mix of products, ensuring the ability to quickly respond and make applications. Some products the Central Life Sciences team recommends include:

  • Altosid® P35 offers 35 days of residual control, with extended-release technology that supports pre-treatment capabilities 15 days prior to flooding (pre-hatch). Baumbach adds that it is “really easy to work with, less harsh on equipment and easily penetrates canopies during aerial applications.”
  • FourStar® Bti CRG features dual-action controlled release technology, helping this larvicide remain effective through wet and dry periods, killing larvae for up to 40 days and 4 floodings. Riles advises applying these products 20 days after initial Hurricane adulticide applications are complete to prevent emerging mosquitoes.
  • Duplex™-G Larvicide delivers a quick kill and long residual control of most mosquito larvae species as a dual-active control solution combining (S)-methoprene and Bti. The product features “Active Booster Release Technology” and can be used in pre-flood treatments.
  • Altosid XR-G® Ultra is a carbon-free (S)-methoprene formulation featuring 28 days of residual control while continuously wet for a more cost-efficient, clean and consistent extended residual larval control.
  • Altosid® XR Extended Residual Briquets are an ideal solution for larvicide applications in areas impacted by weather that will present limited access opportunities for control teams with the slow-release control of mosquito larvae for up to 150 days. “Knowing that you have 150 days of control in that source- you can't put a price tag on that,” said Elkashef.

“Central Life Sciences were the pioneers and the experts when it comes to IGRs [insect growth regulators] and as such we have developed a lot of products that can fit your specific situation and the habitats you're treating," said Elkashef. “Whether it's granular products or liquid products, whether it's single-brood or multi-brood products, whether it's areas where it's continuously flooded or areas that cycle between wet and dry periods. We have an IGR that can cover you, and our team can help guide you to what might best fit your program and your situation.”