These long, gangly looking insects look like giant mosquitos but they are completely harmless (they neither bite nor sting). Their off spring (leather jackets) can cause some serious damage though, (if in sufficient numbers), to the roots of lawns and other garden plants.
European Crane Flies (Tipula paludosa Meigen)
Crane Flies (sometimes called daddy-long-legs or mosquito hawks) are long and gangly, two winged flies that look like giant mosquitos. They are week fliers and are attracted to moist habitats. Adult males are 14-19 mm long, adult females are 19-25 mm long. They are light brown to grayish in colour and tend to congregate on the sides of buildings and window screens.
European crane flies emerge from the soil, after sunset, in late summer (late August to mid September). Typically within 24 hours after their emergence they begin mating. Mating occurs on the foliage of the turf grass. The impregnated females then deposit approximately 300 eggs into the upper soil level 1/2″) and die shortly after. The eggs which are oval and black in colour require moisture and a temperature of at least 14 degrees Celsius in order to hatch. Under these ideal conditions they will hatch within 2 weeks.
Are the larvae of crane flies. They have a tough leathery outer skin, thus their name, which is light grey to brown in colour. Leatherjackets look like short, fat, brown worms . However when stretched out from their usual contracted state they can measure approximately 4cm (1 1/2″) long.
Leatherjackets begin feeding in the fall (August/September) soon after hatching. They use their rasping mouthparts to feed on plant roots, rhizomes and foliage. They over winter in the soil then continue their feeding frenzy in the spring. In milder winters they can continue to feed through some or part of the winter. (Note: Although leatherjackets over winter many do not survive the winter especially if they are exposed to cold, dry conditions.) This feeding frenzy lasts until early summer (late May to mid June) when they cease feeding, move down into the upper soil profile (3-5 cm deep) and remain in a non-feeding stage until pupation. Pupation occurs from late August through early-to-mid-September, when the pupae wriggle to the top of the soil in the late night to early morning and the adults emerge (omafra (2013)).
Note: the vast majority of crane flies in Canada and the U.S.A. are European.
Common Crane Fly (Tipula oleracea)
Differ from the European crane fly in that they have 2 generations per year. “Overwintering larvae from the previous fall pupate in February-March and emerge as adults in late March-April. Mating takes place and eggs are laid. The second generation of larvae mature from April through September and adults emerge for the second generation at the same time as the one generation European from August through September” (Nutri Lawn (n.d.)). The wings on the common crane fly are longer than the body and it’s females can fly farther to distribute their eggs than European crane fly females. (Oregon State University (n.d.).
The leather jackets feed on the roots of turf and other garden plants. They also chew the grass blades. Turf damage appears as yellow spots and thinning bare patches. The turf in these areas pulls up easily. Secondary pests like skunks, racoons and starling damage turf digging for the leather jackets. Damage is similar to grub damage except the leather jackets do not destroy all of the roots as grubs do.
- Keep the lawns on the drier side at egg laying time.
- Improve drainage. Since crane flies are attracted to moist habitats make sure your soil is draining freely.
- Encourage birds to visit your yard. They love to feed on the leather jackets and do a decent job controlling populations.
- Monitor your lawns regularly for signs of leather jacket damage.
- Hand picking (or vacuuming) is an option if your populations are low. They reside in the upper surface of the soil by day but on damp evenings and cloudy days the come to the surface to feed on the leaf blades. That is the best time to pick or vac them.
Beneficial nematodes (Steinernema feltiae)
Are a safe, natural way to provide some control to leatherjacket populations. Researchers have found them to be about 55% effective (Oregon State University (n.d.)). These microscopic, parasitic, non-segmented worms, (which occur naturally in soil all over the world), seek out the leatherjackets and attack the pest by entering natural body openings or by penetration of the body wall. Once inside, they release a bacterium that kills the host within 48 hours. The nematodes then continue to reproduce inside the dead pest and release a new generation of hungry nematodes, which set off in search of further prey. Nematodes are not harmful to birds, animals, people or plant life.
The best time to apply these specific nematodes is in spring when the soil temperature is above 12ºC (54ºF) and in the fall as soon as the eggs begin to hatch. Apply to moist lawns and keep continuously moist for about 2 weeks. You can find nematodes at larger garden nurseries in the refrigerated section or by mail order. Read the label carefully for storage, application and specific hosts it is effective against.
Chemical Control For Home Owners
For regions permitted the use of chemicals Visit Pacific Northwest Extension Publication, ‘Turfgrass-Crane fly’ for a list of chemical controls available. Be sure to check with your region first to see what is lawful for you to use.
Photo Credits: photos by the Author.
OMAFRA (2013), ‘European Crane Fly’, Retrieved on Jan.17, 2021 from: http://www.omafra.gov.on.ca/english/crops/facts/13-023.htm
Oregon State University (n.d.), A Pacific Northwest Extension Publication, ‘Turfgrass-Crane fly’, Retrieved on Jan. 17, 2021 from: https://pnwhandbooks.org/insect/hort/turfgrass/turfgrass-crane-fly
Nutri Lawn (n.d.), https://www.nutrilawn.com/leather-jackets
Site One Landscape Supply (n.d.). Leatherjacket. https://www.siteone.ca/home/resources-services/technical-support/leatherjacket.aspx
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