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Treehole Mosquitoes, Control Measures, and Requests for Service

Spring is the prime time for the emergence of Aedes sierrensis, the western treehole mosquito. These mosquitoes lay their eggs in cavities of oak, bay, and several other types of trees. Treehole mosquito larvae can also be found in discarded tires or containers where plant debris and water has accumulated. Residents living in areas with dense populations of trees or adjacent to recreational areas and open space may experience large numbers treehole mosquitoes. They can be aggressive bitters during the day and evening. 

While these mosquitoes are currently not known to transmit pathogens to humans, they can cause severe discomfort and transmit canine heart worm to your dog. 


Ways you can control treehole mosquitoes on your property:

  • Inspect trees for holes, including holes as small as ½” that lead to cavities that may hold water. Contact a licensed arborist to discuss appropriate measures to prevent water from accumulating in treeholes.
  • Remove buckets, toys, tarps or other items holding water.
  • Check your gutters for clogs and standing water.
  • Contact the District for help reducing mosquito populations on your property.
  • For temporary relief from treehole mosquitoes in your backyard, try using one or more oscillating fans pointed away from seating areas. Treehole mosquitoes are weak flyers and have difficulty flying against the wind generated by the fans.


MSMVCD Control Measures and Requests for Service

Because cavities in trees utilized by these mosquitoes are inaccessible, effective control in the larval stage is not possible.  In an effort to provide relief to residents and to reduce treehole mosquito numbers, we will be conducting adult mosquito control applications on individual properties, as requested, and after the proper surveillance has been conducted.

Our technicians are responding to service requests as quickly as possible given the extreme volume of calls and difficulty with communication given the current social distancing protocols.

The District will be contacting residents in the immediate vicinity of adult mosquito control applications utilizing one or more of the following methods:

  1. By knocking on doors and contacting residents in person while practicing appropriate social distancing.  Our staff will be wearing masks.
  2. Leaving an informational sheet on residents’ doorsteps.
  3. Informational calls through the District’s Everbridge system when feasible (sign up here)
  4. Posting information on Nextdoor Community forums

Thank you very much for your patience and cooperation while we work to reduce the numbers of adult mosquitoes and the discomfort you are currently experiencing during these challenging times.