Floodwater Mosquitoes

A wet spring has left water standing in low areas across the state. This sets the stage for problems with floodwater mosquitoes over the next few weeks. That potential is greatest in the dark blue and dark green areas on the map (Figure 1).

Floodwater mosquitoes are not considered to be major disease vectors, but they can carry dog heartworm. However, their painful bites can make outdoor evening activities very unpleasant.

Figure 1. Rainfall (inches) during the past 21 days ending 4/17/15 . (Photo: UK Ag Weather Center)

Figure 1. Rainfall (inches) during the past 21 days ending 4/17/15 . (Photo: UK Ag Weather Center)

Eggs of floodwater mosquitoes were laid last summer on soil in low areas where excess water pooled.  These dormant eggs hatch after water from spring rains warms to 70°F to 80°F.  Then the larvae (wrigglers) can complete their development and emerge as adults in as few as 7 to 9 days. Cool temperatures have slowed development for a time, but growth will increase when sunny skies return.

The inland floodwater mosquito (Aedes vexans, Figure 2) is very common in western Kentucky. This aggressive mosquito has a painful bite and can travel more than 10 miles from its breeding site, causing problems over an extended area.

Figure 2. Aedes mosquitoes (Photo: Ary Farajollahi, Bugwood.org)

Figure 2. Aedes mosquitoes (Photo: Ary Farajollahi, Bugwood.org)

The inland floodwater mosquito rests during the day on shaded vegetation and in tall grass. Feeding is typically concentrated beginning about an hour before sunset until 2 hours after dark. However, walking through a resting site during the day can stir them up. This serious nuisance pest can carry some virus diseases and dog heartworm. While the inland floodwater mosquito apparently prefers humans, it is an opportunistic feeder. Other mammals and birds can provide a needed blood meal.

The dark ricefield mosquito (Psorophora columbiae) is a large dark mosquito with yellow or white markings. It is a serious nuisance to humans and livestock.  It develops in temporary freshwater pools, such as grassy roadside ditch banks.


  • It is always a good idea to eliminate as many mosquito breeding sites around a property as possible. However, the long flight range of the floodwater species limits the value of this tactic.
  • Repellents provide some protection from mosquito bites. Those registered with the EPA (Environmental Protection Agency) containing DEET, picaridin, IR3535, and some oil of lemon eucalyptus and para-menthane-diol tend to provide long-lasting protection. Most products containing these active ingredients can be used on children. However, products containing oil of lemon eucalyptus should not be used on children younger than 3 years old. Reapply the repellent as necessary when mosquitoes start to bite.


By Lee Townsend, Extension Entomologist



Posted in Human Pests
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