European Crane Fly (Tipula Paludosa)
European Crane Fly (Tipula Paludosa) is a native of Western Europe that was introduced to eastern Canada and found in British Columbia in 1965. It's the most common pest in Oregon lawns. The Pacific Northwest is ideal habitat for this insect with its mild winters, cool summers and abundant rainfall. Adults are a winged insect that looks like a very large mosquito. ECF emerge, mate, lay eggs and die in early September. They have a short lifespan of 2-14 days. Mating and egg laying usually happen within a day. Eggs take 11-15 days to hatch. Adult ECF do not feed on or cause damage to grass. Adult Common Crane Flies (Tipula oleracea) look like ECF but are far less abundant. Common Crane Fly emerge twice a year but are not associated with turf damage.
The larvae are about an inch long, wormlike, and have leathery skin. The larvae are sometimes referred to as leatherbacks. Larvae damage turf in late fall and into late spring as they feed. Most damage occurs in December, April, and May. ECF larvae feed primarily on shoots and crowns, but also feed on roots. Healthy lawns can tolerate 25 - 50 crane fly larvae per square foot without significant damage. Damaged turf looks brown from the dying grass. Patches of dead grass can expand quickly as the larva feeds. If brown patches appear in the middle of summer irrigation is more likely an issue.
Successful hatching of ECF eggs is highly dependent on moisture. Eliminating irrigation while the eggs are on the soil and hatching is an effective cost saving deterrent. The challenge with this strategy is that the eggs hatch during the grass's growing season. During this time efforts are made to catalyze growth and re-establish turf with irrigation, and overseeding before the grass goes dormant.
Birds feed on crane fly larvae so if the canopy of a lawn is open enough birds can control larvae populations. Lawns with excessive thatch offer excellent protection and habitat for ECF larvae. Maintaining low levels of thatch will minimize the possibility and extent of ECF damage.
Predatory nematodes are a safe non-toxic means of controlling ECF larvae populations. Timing and soil temperatures are important when applying predatory nematodes. Even with proper conditions predatory nematodes are not likely to kill all the larvae but, killing a significant portion of the larvae with nematodes may be all that is needed.