Water Garden Mosquito Control


Whether you have a water garden or thinking of building a water garden, the question is always, what about mosquitoes. How do I control mosquitoes? Will having a water garden become a magnet for mosquitoes? Doesn't a water garden become a breeding sanctuary for mosquitoes? Mosquitoes carry diseases like the West Nile virus, heart worm, malaria, encephalitis, and many others. The females, who drink blood, can carry disease from one animal to another as they feed. The female will lay from 40 to 400 eggs that can become adults in 5 - 14 days and it does not take long to have a serious problem.


Constructing a water garden does not have to be a breeding ground for mosquitoes. The first thing to consider when constructing a water garden is water movement. Mosquitoes only lay eggs in stagnate shallow water. Having good surface water flow is the most important thing to consider. When designing your water garden or koi pond think in terms of a beginning and end of the surface water. The beginning can be a waterfall or stream. This not only creates a lot of surface water movement, but also adds oxygen to the water. And nothing is more soothing than the sound of the trickle of water in a stream or the splashing of a waterfall. The end should be a good pond skimmer. A skimmer will not only sweep most mosquito larvae into its mechanical filter, but will also keep the surface clean, giving the larvae less to eat. Care should be taken not to have plants take over the surface of the water. Even though you may have sufficient water flow, plants like water lilies and parrots feather can cover too much of the water surface and create stagnate areas in the water garden. A fountain or spitter can help, and most water plants will enjoy the water splash except for water lilies. Water lilies should be planted far enough from the edge to allow water to flow around. Still, you may have to pipe water to edges of the water garden where there is not enough surface movement. Sufficient drainage should be installed to prevent puddles from heavy rains when the pond overflows. Remember, eggs can become adults in 5 - 14 days.


Natural Control

Any water garden or koi pond will attract predators that will feed on mosquitoes and their larvae. Dragon flies and damselflies have an insatiable appetite for mosquitoes and their larvae prey on mosquito larvae. Toads and frogs also prey on mosquitoes and tadpoles eat mosquito larvae. Other predators include water striders, also called water skippers, that eat mosquito larvae.

lepard frog
water strider

Small fish are very instrumental in keeping mosquito populations in check. Fathead minnows are a proven method to reduce or eliminate mosquito larvae from ornamental ponds, stock ponds, and other semi-permanent to permanent water. Fathead minnows are able to feed in heavy aquatic vegetation and in small pockets where larger goldfish and koi cannot reach. They can withstand up to 80 degree water and will reproduce up to 4 times per year under optimal conditions. It is recommended to place between 250-500 minnows per surface acre of water (This equates to 1-2 minnows per 10 foot by 10 foot area, but adding a few more for a tiny pond does not appear to be detrimental). Fathead minnows can generally survive winters unless the pond is too shallow and freezes completely over. Rosy red minnows are fathead minnows that have been bred for the orange red color. Both the fathead and rosy red minnows are readily available at pet stores. Mosquito fish are known for their appetite of mosquito larvae if you can find them locally. They are not as hardy in colder climates as the fathead minnow or the rosy red minnow. Guppies can also be used and breed rapidly, but don't expect them to survive winter. All of these fish can be used in any water garden from the whiskey barrel to a large koi pond. Since koi and goldfish do not prey on other fish they can be kept together with no problems.

rosy red minnow
fathead minnow

Biological Control


Bacillus thuringiensis subspecies israaelenses (BTI) acts to kill mosquito and black fly larvae for 30 days or more. This bacteria will not hurt pets, birds, fish, or plants. BTI can be used in bird baths, ponds, flower pots or in any standing water where mosquitoes may lay eggs. Mosquito dunks and mosquito bits float on the surface. Mosquito dunks cover a 100 square foot area and mosquito bits are great for bird baths, whiskey barrel, and other small water features. Microbe-Lift has a liquid BTI and a 6 ounce bottle will treat 2,500 gallons for 7 months.

Mosquitoes have a maximum adult life span of 30 days. Creating a water garden that prevents larvae from becoming adult mosquitoes could actually be instrumental in controlling the population in your area. It certainly won't add to the problem and the enjoyment from having a water garden or koi pond will last for many years.