Natural predators have a role to play in mosquito control, but by themselves, they probably won’t be able to control all of your mosquito population – especially if the population is exceptionally large, as may be the case after a hurricane or period of particularly hard rain. When there are high rates of mosquito borne diseases – West Nile Virus for example – you may want to pursue mosquito elimination more aggressively.
Unfortunately, while there are a number of anecdotal claims about the effectiveness of natural predators, there’s very little hard scientific evidence. In addition, the studies that do exist generally took place in a controlled environment which can’t accurately mimic natural conditions. And, of course, it would be difficult to measure changes in the number of mosquitoes living in any given section of nature – at least not with any type of scientific accuracy.
Still, natural predators certainly aren’t harmful and they’re likely beneficial to the local environment, so there’s no reason not to encourage predators known to prey upon mosquitoes. These natural predators are usually most effective in ponds and canals, where the habitat can support a wide variety of wildlife that feeds on insects.
Where there are bodies of water, the “mosquitofish”, or Gambusia affinis, is a good choice. This fish is a voracious predator when it comes to mosquitoes. In fact, it’s been said that they can consume from half to one and one half times their body weight each day in small invertebrates like the larvae of mosquitoes. The fish bears live young – up to three to six broods each season – with from 10 to 300 fry per broods. For this reason, a number of mosquito control districts have used this natural predator with great results.
Conversely, the ability of the purple martin to control mosquitoes has been greatly overestimated. Yes, these birds do eat mosquitoes, but they make up only three percent or less of the martin’s diet. Martins primarily feed during the day, which isn’t when most mosquitoes are most active. They also feed on other natural predators of mosquitoes, including dragonflies. Purple martins are a better choice if you have a problem with Japanese beetles.
The ability of the bat to control mosquitoes is often overestimated, as well. Bats will eat mosquitoes if they’re there, but they don’t generally go out of their way to seek them as a preferred food source. While they may not be the best choice for getting rid of mosquitoes, they do help control a number of other harmful pests, and are considered to be beneficial animals when they make their home in your yard or garden.
Dragonflies are another natural predator of the mosquito and while they consume their fair share, again, they don’t kill mosquitoes in numbers that will make a significant change in the local population. However, dragonflies remain in their aquatic larval stage for quite some time – up to six years – and during this time they can make a dent in the local population of mosquito larvae.