Crane flies also known as mosquito hawks or daddy longlegs look like large oversize mosquitoes. These are the large, clumsy insects which fly around our gardens in late summer and early autumn. They are often seen bumbling along the ground, getting trapped in windows and flying into our faces when we least expect it.
Identification: Crane flies are grey to brown in colour, about 15 mm to 25 mm long, have a long, slender body with thin, smoky wings and extremely long legs. They do not bite or cause any harm but can be very annoying. Crane fly larvae are cylindrical, and look like worms, growing up to 4 cm long. They are often called leatherjackets, due to their tough skin.
Habitat: Adult crane flies are most active near twilight. They commonly occur in in moist damp environments because the larvae need moisture to survive. They’re attracted to moist areas, including irrigated lawns. Some larvae are aquatic while others get enough moisture from the soil or mud.
Diet: A couple of the crane fly species drink nectar and serves as pollinators but most of them do not eat anything as adults. Most adult crane flies sustain themselves mainly on what they ate, and the food stored during their larva phase. The adult crane flies only constitute a nuisance. Also, adult crane usually lives for a couple of days and dies. Larvae can live up to a year and it is the larval stage which is of concern. These larvae can cause havoc to the lawns or yard. The larvae (leather jackets) live in crevices during the day and come out at night for feeding. The diet of leather jackets include grass, fruits, flowers, vegetables, sprouts from seeds and crop roots. Affected plants die suddenly. Lawns can be devastated.
Life cycle: Adult females lay their eggs on scrub grassland and on lawns. These eggs hatch into grubs (the leatherjackets) two or three weeks later, depending on the climatic conditions. These grubs move through the soil and attack the roots of plants around them. During winter they dig deep and undergo hibernation and start up again in the spring. In late spring the grubs pupate and transform over several weeks into the adult crane fly.
Signs of crane fly damage: Leatherjackets feed on all parts of grass plants from the roots and crowns to the blades. Feeding is heaviest in fall, right after the pest hatch, and again in spring when they start feeding on grass again. Damage is most obvious in spring, as fall-damaged grass thins, and irregular brown patches begin to die.
How to identify if it is a crane fly larvae damage?
First thing is to find a patch of dead or dying grass in your lawn. Grab a handful of grass in this area and try to pull it up. Healthy grass will not budge, being held in place by the roots. Grass subjected to a heavy grub attack will come away easily, almost like a carpet. Next, use a shovel to separate the damaged grass layer from the soil, and have a look to try to identify a grub. There are mainly four different types of soil grubs found in New Zealand- leatherjackets, chafer grubs, cutworms or wireworms.
Identification of different grubs: Wireworms are thin and orange. Cutworms are quite large, ‘C’-shaped blue-grey caterpillar type grubs. Chafer grubs are white, usually curled up in a ‘C’ shape with a black head. Leatherjackets are darker coloured, straight and can be between 0.5cm to over 2cm long.
Most adult crane flies are only annoying, but they are not harmful to humans or plants. Therefore, control measures should be focused on getting rid of crane fly larvae. Following precautionary steps can help prevent their spread:
- Keep your Lawn Dry:Since most crane flies thrive in a wet environment, try as much as possible to keep your lawn dry. Avoid wetting your grass too much, only sparingly
- Get Rid of your Lawn Thatch: eliminate that dead grass that has built up in your lawn. Those thick thatch on your lawn can hinder your plant from getting a good air and obstruct water movements. Good aeration of soil is important. This makes the root of your soil more porous, allowing easy movement of water.
- Increase moving frequency to prevent the eggs being laid in the soil: In late summer, when the adult crane flies are flying around is when the next generation of leatherjackets are being produced. The adults do not live for very long and their only task is to mate and lay eggs. Preventing these eggs from getting into your soil will drastically reduce the chances of a leatherjacket attack the following winter. Increase your mowing frequency and collect all the grass clippings. Even if the grass it doesn’t need mowing! This will remove a lot of the crane fly eggs from the surface of the soil before they germinate.
- Keep your lawn strong: If your lawn has not yet been attacked then you can minimise damage to grass by keeping it as healthy as possible. Grass with a shallow, weak root system will struggle with an insect attack. Deep roots from a strong, seeded lawn will be better equipped to cope and re-grow lost root mass. Aerate your lawn regularly and keep to a quality feeding programme to keep the lawn as healthy as possible throughout the year.
Are crane flies Mosquitoes?
Crane flies are not mosquitoes, but they are sometimes referred to as ‘mosquito hawks. They just look like giant mosquitoes with their long skinny legs and long wings but are quite harmless and do not bite, sting, or suck blood but can be very annoying if the population is very high.