Mosquito Control:  Starting in the Swamps

 

Mosquito control starts in the swamps, marshes, seepage ponds, and any other area that holds shallow stagnant water.  To understand why water is critical to mosquitoes, one must understand the mosquito life cycle.

 

Mosquitoes have four distinct stages in their life cycle: egg, larva, pupa, and adult.   

 

Depending on the species of mosquito, eggs are laid either singly or attached to each other in groups of 50-200 eggs.  When the eggs are joined, they are called an egg raft.  Most mosquitoes lay their eggs directly on the water surface where they hatch into larvae a couple of days later.  There are also some mosquitoes which lay their eggs on the ground next to the water.  When the water rises from increased irrigation, snow melt, etc., the eggs hatch and the larvae emerge.  Regardless of the mosquito species, all larvae require water to survive.

A mosquito larva, as seen through a microscope.  
Photo credit: Christina Johnson, GCMCD

Once the larvae emerge from the egg they begin filter feeding.  At this point in their life cycle they feed only on microorganisms and small organic material in the water.  The larvae breathe through a siphon tube that penetrates the water surface.  During their larval stage, the mosquitoes will shed their skin and molt four times before changing to the pupal stage of their life cycle.

Mosquito pupae resting just below the surface of the water.

 

The pupal stage is where metamorphosis occurs, creating the adult mosquito.   During the pupal stage they are no longer feeding as they have ingested enough nutrients to make the transition into an adult.  This phase of the life cycle is similar to the cocoon of a butterfly although the mosquito pupa is fully active and mobile.  Alike the larval stage, the pupal stage of a mosquito is entirely aquatic, and the mosquito will perish if it is removed from the water.

 

 

The adult stage the portion of the life cycle most people associate with mosquitoes.  The adult stage is the only stage in their life cycle in which they are not fully aquatic, and the only stage in which they take a blood meal.  After emerging from the pupal casing, the newly hatched adult will rest on top of the water to dry its wings and body.  Once dried, the mosquito is capable of flight.  

 

While it varies based on temperature and mosquito species, it can take only seven to ten days for a mosquito to go from egg to adult.

 

With the basic biology of mosquitoes addressed, we can get into the details of how GCMCD program works. 

 

Here at GCMCD, the vast majority of our applications target mosquito larvae.  The products used to kill mosquito larvae are extremely low in toxicity and do not affect other aquatic organisms.   

 

While Moses Lake is a desert, there is an abundance of mosquito habitat.  This is due to the introduction of irrigation to the Columbia Basin along with natural waterways throughout the district.

 

To determine if an area is breeding mosquitoes field technicians sample the habitat using a dipper.  A dipper is a small white cup attached to a long wooden handle.  The dipper is used to skim the water surface and the technician analyzes the sample taken for the presence of mosquito larvae and/or pupae.

A field technician sampling water for the presence of mosquito larvae.

 

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