A sample of alfalfa plants from Muhlenberg County was submitted by Darrell Simpson (Agriculture & Natural Resources Agent in Muhlenberg, KY) to the Plant Disease Diagnostic Laboratory at the University of Kentucky’s Research and Education Center in Princeton on March 26, 2019. These plants showed signs of injury to the stems, foliage, and roots. The agent indicated that an abundant number of larvae were present on the plants in the field when collected. This was confirmed in the lab following further examination. An abundant number of crane fly larvae were found in the soil (Figure 1A). Roots showed signs of secondary root feeding (Figure 1B). In addition, stems, young foliage, and shoots seemed to be damaged by crane fly larvae (Figures 1C and 1D).
Description of Crane Flies
Adult crane flies are relatively large insects with wing spans that can be larger than 1 inch. They resemble “giant mosquitoes” (Figure 2). Usually they emerge in summer to mate and lay their eggs in the grass. Larvae hatch and live in moist soils or decomposing vegetation; they feed on roots or decaying organic matter. They overwinter as pupae or larvae under similar environmental conditions. Larvae of crane flies (also known as leatherjackets) have a tubular shape; however, when retracted, they can be oblong. The posterior end of crane fly larvae have spiracular discs and retractable anal papillae (shown on Figure 2b).
Crane fly larvae are sporadic problems in forages and lawns, especially in cool-season pastures. The presence of abundant crane fly larvae in fields in Kentucky in 2019 might be due to the wet winter season observed. Control actions are rarely required.
A diagnostic tool used in lawns is to conduct soapy water flushes to determine the numbers of larvae present. In Utah, the action threshold is 25 to 50 larvae per square foot.
- Crane Fly Larvae in Turf (NC State).
- Morphology and terminology of Diptera larvae. Courtney, G.; B. J. Sinclair, and R. Meier. In: Papp L., Darvas, B. (eds). Contributions to a manual of Palaearctic Diptera (with special reference to flies of economic importance). Volume 1. General and applied dipterology. Budapest, Science Herald, pp.: 75-163.
- Crane flies (UK Critter Files).
- Common crane fly. (Utah Pests fact sheet)
- Got Big, Gangly-legged Flies? (KPN 03-22-16)
Raul T. Villanueva, Extension Entomologist and Brenda Kennedy, Plant Disease Diagnostician