Crane Fly Larvae in Turf
Adult crane flies (Tipula spp.) are large insects that resemble giant mosquitoes (Figure 1). Although the crane fly wingspan may be two inches across, they are clumsy and weak fliers and can often be seen resting on the side of a building or structure. Crane fly larvae, or maggots, are approximately 2-3 inches long and have no legs, unlike caterpillars (Figure 2). Over time, the larvae develop a tough outer skin and can sometimes be referred to as “leatherjackets”.
Although intimidating looking due to their large size, crane fly adults cannot bite and are not associated with transmitting human diseases. Crane fly larvae, however, can cause damage in a number of field crops including turf, pasture, forestry and agricultural crops beds.
Crane flies emerge in summer, fly, mate, and lay their eggs in the thatch of the grass. Eggs hatch and small, brown larvae feed throughout the fall until they overwinter. As temperatures increase in the spring, larvae continue feeding and maturing. In early summer, larvae pupate just below the soil surface.
Crane fly larvae chew on the roots and crowns of the turf and larger instars will come up at night to feed on the foliar tissue. Damage is usually more noticeable late fall and in spring when larger, overwintered larvae have resumed feeding. Damage typically starts as a general thinning of the turf which progresses to larger, brown patches (Figure 3). Unless they occur in large numbers, crane flies are considered nuisance pests on golf courses.
Proper mowing and fertilization to encourage a healthy turfgrass stand will minimize the likelihood of a crane fly infestation and help turf outgrow damage as it occurs. Avoid irrigating the turf under wet conditions if eggs are present and provide better drainage for chronically wet areas. Allowing the grass to dry will increase the likelihood of egg desiccation (drying out). Remove excess thatch to minimize habitat areas for crane fly larvae.
Birds, ground beetles and parasitic organisms can reduce crane fly populations in areas with fewer inputs. Applications of the insect-parasitic nematode Steinernema feltiae may give up to 50% reduction when properly applied.
Crane flies are generally more of an issue in the northeast, particularly in cool-season grasses. Control measures are rarely required in North Carolina. Soapy water flushes may be a good diagnostic tool for determining the size of maggot populations.
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