New interest in mosquitoes

A simple bucket with leaves and compost becomes a
mosquito breeding site (see inset) after a rain. Photo
by M. Merchant in his own backyard (oops).

After last summer's West Nile virus epidemic in north Texas there is a heightened awareness of mosquitoes and mosquito issues around the state.

Every pest management professional, especially anyone involved with residential pest control, should think of mosquitoes as an opportunity to provide another valuable customer pest control service.

In my experience, few people imagine that they might be the culprit when it comes to breeding  mosquitoes.  Most folks believe that mosquitoes come from someone else's property--especially the creek across the street, or the neighbor's fish pond.

While this might be true, especially in the case of an abandoned pool or marshy area, we are often our own worst enemy. Most creeks, ponds and lakes are not major sources of disease-carrying mosquitoes.  Any body of water with fish, or with running water that is not stagnant, is not likely to be an important breeding site for the worst mosquito species--most of which are "container breeders". Rather, small containers or human structures that collect dust and debris along with water that sits for more than a couple of weeks, are the most likely source for our worst disease transmitting mosquitoes like the urban-dwelling Aedes and Culex species.

A few years ago, Dallas County did an evaluation on the properties of citizens who reported severe  mosquito problems in their backyards.  They found that 25% of citizens who complained about mosquitoes were  breeding mosquitoes in containers found in their own yards.

Green pools are common in neighborhoods with
foreclosed homes, and should be drained or
treated. Photo by M. Merchant

As a PMP you approach every property with trained eyes to see pests and to see conditions that are conducive to pest infestation. This skill can serve you well when inspecting a backyard for mosquitoes, and provide value-added to any pest control visit.  Here are some of the common problem areas to be alert for in residential yards:

• Water- and leaf-filled bird baths.  Bird baths should be emptied or cleaned weekly to minimize risk of mosquito breeding.  
• Gutters that fail to drain properly.  This can be difficult to see, but your extension mirror can help. Check gutters, especially after a rain, to make sure they are draining properly.  Leaves and dirt that build up in gutters provide the organic matter, all they need is water to make a mosquito breeding spot.
• Tires. Rubber automobile tires, it seems, are designed to hold water.  They are one of the worst sources of mosquito breeding in some areas.
• Buckets, plant pots and wheelbarrows without drain holes. These items should be inverted or hung to ensure that water is not held.
• Landscape and gutter drain lines that catch and hold water.  Poor installation of underground drain pipes allow water to stand.  Mosquitoes are adept at finding their way in and out of underground holes that we may not notice.  All underground drain lines should be fitted with a pop-up drain emitter that opens only when water is flowing.
• Water catch basins/septic tanks.  Catch basins in French drains and municipal storm sewers are designed to keep debris from clogging drain pipes.  But these same boxes can catch and hold water for extended times. Flush out catchment basins or apply a larvicide like Bacillus thuringiensis or methoprene.  Poorly closed or maintained septic systems can provide many breeding sites for Culex mosquitoes.
• Uncapped steel fence posts are often overlooked, but may hold water for long times after a heavy rain. Point out fence posts without covers and explain how any container that holds water can breed mosquitoes.
• Plastic or canvas covers on boats or trailers.  Tarps or plastic sheets used to cover vehicles or boats can easily hold water for a week or more.  Boat covers should be pulled taught to force water to drain.
• Rain barrels and cisterns. With most areas in Texas water is increasingly precious. Drought and water restrictions have encouraged many homeowners to install cisterns and rain barrels to capture and store rain water. While most commercial rain storage systems come with drains to keep mosquitoes out, screening on intakes and overflow plumbing can become damaged, and needs regular inspection.  
• Unmaintained swimming pools.  So called, "green pools" are unchlorinated pools that can become breeding sites for large numbers of mosquitoes.  If you notice such a pool and the homeowner is absent or unwilling to respond to complaints, these sites should be reported to the local health department as a public health threat.

Let's all do our part to keep our communities safer and mosquito free. Let your customers know when they have a dangerous situation.  Chances are that they will thank you for it.  For more information on mosquitoes in backyards, see the Mosquito Safari website.  

Legislative Note

Last week the Texas Senate gave thumbs up (28-3 vote) on a measure (SB 186) introduced by Sen. John Carona (R-Dallas) that would give municipal health officials authority to enter empty or abandoned properties to treat mosquito breeding sites that pose a public health nuisance. It can be difficult for health authorities to gain access to such properties without a search warrant.  This bill would allow a "public official, agent or employee charged with the enforcement of... laws" to enter the premises at a reasonable time to inspect or treat the nuisance stagnant water.

David Oefinger, with the Texas Pest Management Association, feels that chance for passage of the bill in the House is pretty good given the lack of opposition in the Senate.