The Crane Fly is often nicknamed the “skeeter eater,” a term based on the misunderstanding that these large, delicate flies prey on mosquitoes. In reality, adult Crane Flies do not eat mosquitoes or other insects; many species only consume nectar or do not feed at all during their short lifespan. The primary concern with Crane Flies is their larval stage, which can cause significant damage to lawns and turf. Effective management requires understanding their life cycle and targeting the destructive stage underground.
Identifying the Crane Fly
Crane Flies belong to the family Tipulidae and are characterized by their long, spindly legs and slender body. They are significantly larger than mosquitoes, with some species having a wingspan up to two and a half inches, and they lack the piercing mouthparts needed to bite humans or animals. Unlike mosquitoes, which fold their wings at rest, the Crane Fly typically rests with its wings spread out.
The larval stage, commonly called “leatherjackets,” is the pest that causes damage to turf and plants. These larvae are grayish-brown, legless, and grub-like, measuring up to an inch or more in length. Leatherjackets feed on decaying organic matter, plant roots, and grass crowns in moist soil, which leads to visible lawn damage.
Targeting the Larval Stage
Leatherjackets are the primary focus for effective long-term control because they cause turf damage and are the source of future adult populations. Key indicators of a problem include irregular brown or yellow patches in the lawn, especially in spring, or increased activity from birds, skunks, and raccoons digging for the grubs. Intervention is recommended if sampling reveals more than 25 larvae per square foot of turf.
Biological control using beneficial nematodes is an effective and environmentally conscious method for targeting these underground pests. The parasitic species Steinernema feltiae seeks out and infects the larvae, stopping them from feeding within a few days. The ideal time for application is in the late summer or early fall (August to October), when newly hatched leatherjackets are small and near the soil surface. Applying nematodes requires moist soil and appropriate temperatures, generally above 55°F, and should be done at dawn or dusk to protect them from ultraviolet light.
For severe or persistent infestations, chemical control may be necessary, involving the use of registered grub or lawn insect control products. These insecticides, which may contain active ingredients such as carbaryl or imidacloprid, are generally applied in the late winter or early spring before major turf damage occurs. Applying these products when the larvae are actively feeding ensures the best results, and the application requires watering the lawn afterward to move the product into the soil where the leatherjackets reside. Following product instructions for application timing and safety is important to minimize impact on pollinators.
Immediate Management of Adult Flies
While eliminating the larvae addresses the root of the problem, adult Crane Flies can still be a nuisance when they emerge and fly around the home. Adult flies are strongly attracted to light, frequently congregating near exterior doors and windows, and often finding their way inside. This short-term annoyance can be managed with simple physical and light-based tactics.
Inside the home, adult Crane Flies can be managed with physical removal methods, such as using a handheld vacuum cleaner to capture them. Placing sticky traps near entry points or windows can also intercept the flies as they move toward a light source. Since they are not harmful, immediate management focuses on nuisance reduction rather than pest elimination.
Managing exterior lighting is an effective way to reduce the number of adult flies congregating near the home. Changing outdoor bulbs to yellow-spectrum or sodium vapor lights makes the area less attractive to nocturnal insects like Crane Flies. Ensuring windows and doors are properly sealed prevents the large fliers from accidentally entering living spaces.
Preventing Future Outbreaks
Long-term management involves cultural practices that make the environment less hospitable for Crane Flies to reproduce. Since Crane Flies prefer to lay eggs in consistently moist or overly saturated soil, proper water management is a primary preventative strategy. Reducing or turning off irrigation in the late summer and early fall, when adults are emerging to lay eggs, can significantly reduce egg survival.
Improving soil drainage is another preventative element, which can be accomplished through lawn aeration to reduce soil compaction and help water move through the turf more efficiently. Reducing excessive thatch buildup provides fewer protected areas for the larvae to develop and feed. A healthy, well-maintained lawn can better withstand the minor feeding damage that might occur even with a low population of leatherjackets.
In areas where damage has occurred, prompt reseeding or overseeding is important to restore the turf and outcompete any remaining larvae. Maintaining a robust lawn through appropriate fertilization and mowing practices ensures that the grass can tolerate and recover from any feeding activity. By focusing on habitat modification and promoting turf health, the likelihood of a significant future outbreak is reduced.