How to Fix Your Pool Mosquito Problem

The recent California drought has raised some concerns throughout the communities there, specifically from mosquito-control officers in the San Joaquin Valley. They are worried that the area may experience some serious West Nile Virus outbreaks in addition to other diseases carried by mosquitoes like dengue and yellow fever.

The potential problem is this: many communities have asked (or even banned) homeowners from refilling their pools because they see it as wasteful. Pools that have been winterized are particularly susceptible to becoming breeding grounds for mosquitos that may eventually transmit disease to humans. Last year, 29 Californians died of neurological complications from the West Nile virus and nearly 800 were infected.

Warm weather during the winter of 2015 has caused mosquitoes to emerge early from hibernation. Homeowners in California have been making panicked calls to mosquito control officers (yes, there is such a thing) and those kinds of departments are getting four times their usual amount of calls. Drought years seem to have a correlation to the increase in cases of West Nile virus.

How to Prevent Breeding

First, you should know a little bit about mosquitoes. Mosquitoes experience four stages of development: egg, larva, pupa, and adult. Females lay their eggs on the surface of still water and eggs are constantly hatching and larvae are developing. Others deposit eggs on the ground or inside of the walls of containers that are then flooded with water. Standing water that rises causes eggs to hatch and the life cycle of a mosquito is then initiated.

Other facts about mosquitoes:

• The larval and pupal stages begin in standing water.
• It takes one week to develop from an egg to a flying adult.
• Mosquitoes mate after emerging from the aquatic stages.
• Females need blood to facilitate egg development.

Breeding Grounds for Mosquitoes

Mosquitoes look to lay their eggs in standing water. A common target is the water that accumulates on top of pool covers. Unused pools that have closed either in the fall or in late spring before being reopened are also target areas.

How to Prevent Mosquitoes Breeding in Your Pool

Swimming pools that are disinfected and filtered (or have movement) are not ideal breeding grounds for mosquito larvae. You can prevent your pool from becoming a hatchery by taking a few steps:

1. Secure your pool cover so that mosquitoes cannot access the water underneath. This means watching for gaps, rips, and tears that can serve as access points.
2. Water tends to accumulate on the top of your pool cover either from rain accumulation or leaks in the material. The top of the cover should be drained regularly to prevent mosquito breeding, once a week at least. You can do this by using a common cover pump.
3. You can also use insecticide products that are made especially for pools and ponds like mosquito dunks. These can be found in hardware and pet stores.
4. If you’re not intending to use your pool again, you can remove the pool, drain it, fill it in, or find another creative way to repurpose the space.
5. Above ground pools that you don’t intend on using again should be taken apart and stored or discarded. Don’t leave an unused liner or cover outside because they collect pockets of water that mosquitoes then use for breeding.

How to Eliminate a Mosquito Problem

If you’ve noticed mosquitos starting to breed in the water, there are some steps you can take to eliminate the problem.

1. Add a larvicide dunk. These products (the same described above in the prevention section) can be used for every 10 square feet of water surface area. An above-ground pool may only need two or three. You replace these dunks every 30 days while the pool is not in use. They float on the surface so can get to them but you can use a small weight to keep them from drifting to the sides of the pools.
2. Maintain the sanitizer levels in the pool. This isn’t a perfect option for everybody, but you can chlorinate and shock your pool on a regular schedule as recommended for your pool and size to keep your water clean. If you use a larvicide, discard them and maintain chlorine levels at least for 24 hours before use.
3. Run the filter. Programmable filters that utilize timers can help you keep on top of this by moving the water in your pool for as little as two to three hours a day. Since standing water is where mosquitoes tend to lay their eggs, movement will prevent them from being able to hatch.
4. Be sure to remove leaves and other debris that floats on the surface of the water. This creates places where the mosquitoes can hatch eggs and breed.
5. Cover your pool tightly during the off season or during long periods of non-use.
6. For a creative solution, some people will stock their pool with mosquito killing fish like gambusia or fathead minnows after the water has been neutralized, although that’s much more common in ponds.