Each spring, homeowners of the Pacific Northwest face the possibility of crane fly damage to their lawns. Or, more precisely, damage caused by the developing crane fly larvae (commonly called leatherjackets). The larvae feed on the roots and blades of lawn grasses, and are most active in March and April.
The adult crane fly, which generally emerges in August, resembles a giant mosquito. Once the pest reaches its adult form it no longer feeds, and is not harmful to people in any way. The adult crane fly may be seen bumbling around porch lights at night, or congregating on the sides of houses in the daylight hours. The crane fly lays eggs in late summer and early fall, and the larvae will hatch and begin to feed again before winter dormancy.
If a crane fly larvae population exceeds 15-25 per square foot, their feeding may cause unsightly dead patches in a lawn. Recent research from local university extension offices suggest the crane fly does not cause as much damage as they were previously believed to cause in the region, but there are occaisonal infestations in lawns. Recommendations for Crane Fly control include removing thatch every few years, and keeping the lawn well drained. Defending against crane fly damage is as simple as maintaining a healthy lawn through proper watering, mowing, and fertilizing practices.
Severe cases of crane fly infestation should be treated in the spring, before the larvae enter their adult life stages. Where excessive crane fly populations cause significant damage to turf areas, homeowners have several options to eliminate these pests. The least destructive means of controlling larvae is through the introduction of beneficial nematodes. These are available from most local nursery and garden centers, and should be introduced after all danger of frost has passed. If Nematodes are not effective, consult your local university extension office for a list of pesticides registered for use in your area.
Crane fly activity is normal on a lawn, and the sight of a few insects should not be cause for alarm. Keep your lawn healthy through regular maintenance and it will effectively resist mosts pests without the need for pesticides.