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Matt Gohlke / Pools

Don’t let neglected pools harbor mosquitoes

Although Dallas and Tarrant counties have been all over the news recently with more than 200 West Nile virus cases each, those of us in Denton County have not escaped, with 118 people infected with the virus as of Thursday afternoon.

According to Bing Burton of the county health department, this gives Denton County the state’s highest per capita rate of West Nile infection. This prompted Denton County to declare a West Nile virus health emergency this week, which means aerial spraying might not be far behind.

Many factors have contributed to this problem, but a chief concern is stagnant water — which serves as breeding grounds for mosquitoes to lay eggs that can produce thousands of mosquitoes in just a few weeks.

While we will never know the exact source of each individual case of West Nile virus, it is likely that neglected swimming pools are partially to blame.


Problem pools

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 to keep mosquitoes from breeding in a pool, 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 for the owner, absentee homeowners, foreclosures, etc. — pool maintenance outweighs the alternatives.

A few alternatives have been used to help keep mosquitoes out of swimming pools:

•  Mosquito Dunks — A Mosquito Dunk is a doughnut-shaped tablet that you put into a body of stagnant water and as it dissolves, it distributes Bacillus thuringiensis israelensis, a bacterium that kills mosquito larvae. One Mosquito Dunk lasts for about 30 days. There are two problems to using Mosquito Dunks in pools: Surface staining from algae is a possibility, and the lack of water clarity becomes a safety issue.

•  Mosquitofish — Although I have no experience with mosquitofish, they have been used with success in other parts of the country. Mosquitofish (Gambusia affinis) are about the size of minnows and eat mosquito larvae. They were used in the New Orleans area after the Hurricane Katrina disaster and have also been used in California during the foreclosure crisis. If mosquitofish are used in a pool, chemicals such as chlorine cannot be added. They carry the same problems as Mosquito Dunks — surface staining and the lack of pool clarity.

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

•  Drain the pool — This sounds like an easy solution, but there are major problems with it. Most pools are not designed to be drained, and doing so can cause structural damage to the pool. Once a pool is drained, it is very difficult to keep it completely dry — because of rain and sprinkler systems.

•  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.

There are certainly neglected pools in the Denton area that continue to contribute to the mosquito problem. If you suspect that a neglected pool is a breeding ground for mosquitoes, you can call the city code enforcement office at 940-349-8743.


Stagnant water elsewhere

Many other sources around a house 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 mosquitoes. Following are some of the other sources of stagnant water:

•  Bird baths — Although they are attractive and attract birds, they also attract mosquitoes. Because a birth bath holds warm and untreated water, it is perfect for mosquitoes. The best solution would be to drain and clean bird baths every two to three days.

•  Fish ponds and water features — Although they can be beautiful, fish ponds and other water features can be ideal breeding grounds for mosquitoes, especially if they are stagnant. If you have a small pond or water feature that is stagnant, it is best to drain it. You might consider using mosquitofish, which have been used in several parts of the country in larger fish ponds and water features that 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 city staff to correct the problem. Also check the street gutters that lead to storm drains, as they can sometimes hold water because of 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 because of debris that needs to be cleaned out, or even possibly a lack of drainage because the gutters need repair or adjustment.

•  Tarps — Tarps that cover boats, RVs and other equipment oftentimes are capable of holding water. Be sure that these tarps are not currently holding water, then check for standing water after each rain.

•  Containers and miscellaneous items — 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. Turn over these containers or drill holes in them to keep them from 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 to improve the situation.

MATT GOHLKE, certified building professional, is the owner of Gohlke Pools and a member of the National Spa & Pool Institute, Aquatech and the Better Business Bureau. His firm has received national awards, certifications and recognitions in the swimming pool industry. He may be reached at 940-387-7521.