Swimming Pools, Stagnant Water, & Mosquitos

Back in 2012, we were dealing with the West Nile encephalitis epidemic being spread by mosquitos. In 2016, the Zika virus (also spread by mosquitos) was in the news. Recently it was reported (Denton Record Chronicle on June 24, 2019) that a mosquito trap in Frisco tested positive for a West Nile mosquito. Regardless of the disease or the year, it is safe to say mosquitos can cause real problems and we all need to do our part to cut down on the mosquito population.

Stagnant water sources (including swimming pools) definitely contribute to this problem. The Texas Department of State Health Services website states: “If there are any places around your home where water collects, you may be raising mosquitos.”

A neglected swimming pool can certainly cause an increase in the mosquito population, as it becomes a breeding ground for mosquitos to lay eggs that can produce thousands of mosquitos in just a few weeks. Owning a swimming pool carries with it a responsibility to provide care and maintenance for the pool. Operating the filter and keeping the water chemistry in balance is the solution, but that does not always happen. As a matter of fact, there is no better solution than to just maintain the pool. Even in extreme situations that make it difficult to care for a pool—such as financial issues, absentee homeowners, foreclosed homes, etc.—pool maintenance outweighs the alternatives. If keeping the pool maintained is not an option, the following have been used to help with the mosquito issue for swimming pools:

Mosquito Dunks

A mosquito dunk is a doughnut-shaped solid item that you put into a body of stagnant water and as it dissolves, it distributes bacterial toxins that kills mosquito larvae. One mosquito dunk lasts for approximately 30 days. There are two problems using mosquito dunks in pools—the first is that surface staining due to algae is a possibility, and the second is that the lack of pool clarity becomes a safety issue.

Mosquito Fish

Although I have no experience with mosquito fish, they have been used with success in other parts of the country. Mosquito fish (Gambusia Affinis) are about the size of minnows and eat mosquito larvae. They were used in the New Orleans area after the Katrina disaster and were also used in California during the foreclosure crisis. If mosquito fish are used, chemicals (such as chlorine) cannot be added. The same problems exist that exist with mosquito dunks—surface staining due to algae is a possibility and the lack of pool clarity becomes a safety issue.

Cover the Pool

Another option is keeping water in the pool and covering the pool, though you must be sure that the pool cover does not hold water.

Draining the Pool

This sounds like an easy solution, except that there are two problems with it. The first problem is that most pools are not designed to be drained and doing so can cause structural damage to the pool. Another problem is that it is very difficult to drain a pool and keep it completely drained—due to rain, sprinkler systems, etc.

Remove the Pool

Although it might seem like an extreme solution, if you no longer use the pool and it has become a liability, you might consider removing the pool.

Other Stagnant Water Sources

In addition to swimming pools, there are many other sources around houses that can contribute to the mosquito problem. The basic rule is that if it can hold untreated water for more than a few days, it can be a breeding ground for mosquitos. Following are some of the other sources of stagnant water:

Bird Baths

Although they are attractive and attract birds, they also attract mosquitoes. Because it is warm and untreated water, it is perfect for mosquitos. The best solution would be to drain and clean bird baths every 2-3 days.

Fishponds & Water Features

Although they can be beautiful, fishponds and other water features can be ideal breeding grounds for mosquitos, especially if they are stagnant. If you have a fishpond or water feature that is stagnant, it is best to drain it. You might consider using mosquito fish, as mosquito fish have been used in several parts of the country in larger fishponds and water features which are too large to drain.

Storm Drains

Storm drains are obviously necessary, but they can become a problem if they do not drain properly.

If you have a storm drain near your house, be sure that it is draining. If it is not, contact your local municipality and they will correct the problem. Also check the street gutters that lead to the storm drains, as they can sometimes hold water due to concrete curbs shifting.

Clogged Rain Gutters

Rain gutters are “out of sight, out of mind”, but many of them hold water for a few days after a rain. This could be due to debris that needs to be cleaned out or even possibly due to gutters not draining and needing repair or adjustment.

Tarps

Boat tarps, RV tarps, and tarps that cover other equipment oftentimes are capable of holding water. Be sure that these tarps are not currently holding water and then be sure to check the tarp for standing water after each rain.

Containers & Miscellaneous

Most homeowners have containers (buckets, unused flower pots, etc.) and other miscellaneous objects (children’s toys, old tires, tree holes, etc.) that are capable of holding water, especially with the recent rain that we received. Be sure to turn over these containers to be sure that they are not capable of holding water.

As you can see, there are many stagnant water sources that have contributed to this mosquito problem, but if we all do our part we can make an impact on the mosquito population.