Crane Flies

Order: Diptera
Family: Tipulidae

Description

Crane flies are often mistaken for mosquitoes owing to their long legs and elongated, slim bodies. Adults are roughly 13 mm (0.5 inches) long.

After hatching from eggs, larvae are small and brown. Mature crane fly larvae are 25.5-32 mm (1-1.25 inches) long.

The gray to brown pupae are roughly 25 mm (1 inch) long and do not feed. Portions of the pupal case often protrude from the soil surface after the adult has emerged.

Quick Facts

  • The larvae of crane flies are typically associated with aquatic and semi-aquatic habitats. Most crane fly species are not considered pests. 
  • Two species of crane fly are considered pests of turfgrass in the United States. They are the European crane fly (Tipula paludosa), and Tipula oleracea, often referred to as the common or marsh crane fly. The European crane fly is an invasive species.
  • Well maintained turfgrass can withstand injury from feeding of crane fly larvae.
adult crane fly

Adult crane fly
David Cappaert, Bugwood.org

Two species of crane fly are considered pests of turfgrass in the United States, the invasive European crane fly and another species commonly referred to as the common or marsh crane fly. Crane fly eggs and larvae require high moisture for survival, and most species reproduce in aquatic or semi-aquatic habitats. There are many options available for managing crane fly populations in turfgrass without the use of chemical controls.

crane fly larva

Crane fly larva
Ken Gray, Insect Image Collection

injury to fir stems

Injury to stems of fir plants caused by crane fly larvae
Petr Kapitola, Central Institute for Supervising and Testing in Agriculture, Bugwood.org

Life History

Within 24 hours of emerging from the puparium in late summer and fall, adult crane flies mate and lay eggs in turfgrass. Each female can lay as many as 200-300 eggs over several days. About one week later, larvae emerge from eggs and remain in soil where they feed on grass roots and crowns. Young larvae feed throughout autumn and overwinter as partially grown larvae in soil. Feeding activity resumes the following spring when temperatures rise. Larvae require high moisture for survival and tend to remain below the ground, but may surface on damp, warm nights to feed. Pupation takes place under the soil surface in spring, with one generation produced per year.

Injury

Crane fly larvae feed on roots, crowns, and other portions of turf above ground. As a result, larvae can injure root systems and scalp lawns. Dying patches of turfgrass are most noticeable in March and April and indicate that a crane fly infestation may be present. As the grass dies, these patches can become invaded by weeds. Turf infested with crane flies will be attractive to birds and skunks, who may cause further damage as they probe and dig in search of larvae.

Monitoring

High bird activity is an indication that crane fly larvae might be present. Surveying should be done in early spring by inspecting turf for damage. Larvae can be monitored by using a shovel to turn over the top 1-2 inches of soil within a one-square-foot area of turf. Another sampling method involves pouring warm water with dish soap on a mowed area of grass. While this method does not require digging into the soil, it may not be as effective. In healthy, well maintained turfgrass, the treatment threshold is 20 larvae per square foot.

Turfgrass should be monitored in the fall, and low-cut grass can be surveyed for pupal cases. In newly seeded areas that have a history of crane fly infestations, preventative insecticide applications are recommended to protect the young plants.

Cultural Control

Turfgrass that receives adequate fertilizer and proper irrigation can tolerate substantial crane fly feeding. Nitrogen applications in the spring can help mitigate damage later in the season, and better drainage is favorable for areas that are consistently wet since crane flies thrive in wet soils. Controlled drought stress on turfgrass during periods of egg laying seems to significantly reduce larval densities. Turning off irrigation systems after Labor Day can reduce the numbers of larvae without damaging the grass.

Growing grasses that require full sun in shady areas will reduce plant vigor and improve survival of crane fly larvae. Consider growing turfgrass species that prefer shade or groundcover over species that require full sun. Bare areas should be reseeded to prevent invasion by weeds. Lastly, aerifying the soil can help improve grass health by promoting root development and improving water and nutrient movement into the soil.

Biological Control

Crane flies have natural enemies such as birds, fungi, and nematodes. The entomopathogenic nematode, Steinernema carpocapsae, as well as the fungus, Beauveria bassiana, can help suppress larvae of crane fly early in the spring when soils are moist. The combination of cultural and biological controls can be an effective combination for crane fly management.

Chemical Control

Crane fly larvae feed on roots, crowns, and other portions of turf above ground. As a result, larvae can injure root systems and scalp lawns. Dying patches of turfgrass are most noticeable in March and April and indicate that a crane fly infestation may be present. As the grass dies, these patches can become invaded by weeds. Turf infested with crane flies will be attractive to birds and skunks, who may cause further damage as they probe and dig in search of larvae.

References

Ramirez, R. & Kopp, K. 2015. Common Crane Fly. Utah State University – Extension. Available https://extension.usu.edu/pests/uppdl/files/factsheet/crane-fly.pdf

University of California. 2009. Crane Flies. University of California – Integrated Pest Management. Available https://www2.ipm.ucanr.edu/agriculture/turfgrass/crane-flies/#:~:text=Susceptible%20Species-,Description%20of%20the%20Pest,within%2024%20hours%20of%20emerging.

Oregon State University. (n.d.). Turfgrass-Crane fly. Oregon State University – Pacific Northwest Pest Management Handbooks. Available https://pnwhandbooks.org/insect/hort/turfgrass/turfgrass-crane-fly