Dragonflies are highly effective natural predators, primarily feeding on nuisance insects like mosquitoes, midges, and gnats. While generally beneficial, large numbers congregating near swimming pools, patios, or other outdoor living spaces can become a considerable distraction due to their territorial flying and sheer presence. Property owners seeking to reduce the local population should modify the landscape to remove the elements that attract them for hunting and breeding. This article details the habitat adjustments and deterrence methods available to minimize their presence around your home.
Making the Area Less Appealing to Adults
Adult dragonflies require specific environmental conditions to hunt and rest. Many species are “perchers,” relying on high, clear vantage points to scan for prey. Removing tall, thin, vertical structures like bamboo stakes, flagpoles, or isolated plant stems eliminates these preferred hunting posts. Removing their favorite high ground forces them to expend more energy flying or to relocate to a better-suited territory.
Dragonflies are powerful fliers but prefer calm, still air for territorial patrolling and efficient hunting. Introducing airflow by installing high-powered outdoor fans near patios or by clearing dense vegetation to create open wind channels can discourage their activity. The increased turbulence and wind speed make it more difficult for them to hover and maintain their hunting patterns, prompting them to seek calmer locations.
Adult dragonflies are active during the day, but their primary food source, such as gnats and mosquitoes, often swarms at dawn and dusk. Adjusting outdoor lighting to use yellow-spectrum or low-ultraviolet (UV) bulbs reduces the attraction of these smaller insects. Minimizing the available food reduces the dragonflies’ incentive to congregate and feed. Furthermore, removing large, flat, light-colored rocks near water features is recommended, as dragonflies use these surfaces to bask and regulate their body temperature.
Controlling Population at the Aquatic Stage
The most impactful long-term strategy involves interrupting the dragonfly’s life cycle by targeting the aquatic nymph stage. Dragonflies begin their lives underwater, where the nymphs hatch and mature, often for several months or years, requiring standing water to lay their eggs. Eliminating unnecessary sources of standing water, such as buckets, clogged gutters, or tire swings, removes potential breeding sites.
In permanent water features like ponds, increasing water movement and aeration can significantly disrupt the breeding process. Many dragonfly species prefer still or slow-moving water for egg-laying, and a strong fountain or aerator creates surface agitation that makes the habitat less suitable. Removing excessive submerged and emergent vegetation, such as water lilies and cattails, is beneficial because nymphs use this foliage for camouflage and as a pathway to climb out for their final molt into adults.
Introducing natural predators into an ornamental pond can also provide effective control of the aquatic population. Small, non-native fish species, such as minnows or gambusia, are voracious predators that will consume dragonfly eggs and newly hatched nymphs. While the bio-larvicide Bacillus thuringiensis israelensis (BTI) is often used to control mosquito larvae, it does not directly harm dragonfly nymphs. However, BTI works by drastically reducing the population of the nymphs’ primary prey, like mosquito larvae and chironomids, which can indirectly lead to a decline in the dragonfly population.
Immediate Deterrence Methods
For immediate, active repulsion of adult dragonflies in a localized area, physical and visual methods can be employed. Installing visual deterrents, such as strips of reflective or holographic scare tape, can be effective against these highly visual insects. The unpredictable flashes of light and movement are intended to disorient and confuse the dragonflies, prompting them to leave the immediate vicinity.
Another method involves using realistic, wind-activated dragonfly decoys placed around the affected area. This technique relies on the instinct of smaller, biting insects, such as deer flies and mosquitoes, to avoid areas where their primary predator is present. Deploying these decoys reduces the population of the dragonflies’ food source, removing their incentive to stay and hunt on your property.
Standard insect sprays containing DEET or picaridin are not designed to repel dragonflies, as they are not biting pests. A simple physical action, such as using a strong jet of water from a garden hose, provides a temporary solution to disperse congregating adults. This method is best used to discourage perching or swarming in a small area, such as a pool deck, pushing the insects to find a less disturbed location.