Crane flies are large, spindly bugs that are usually seen in late summer. They often invade houses and look a little like big mosquitoes, which many folks find alarming.
Let’s face it; no-one likes them. But are crane flies dangerous? Will they bite you, bug your pets, or damage your furnishings? And what are their larvae likely to do to your lawn?
The good news is that crane flies are completely harmless to people and animals. The bad news is that they may not be so gentle on your lawn, and could cause significant damage to your turf.
What are crane flies?
Crane flies (AKA ‘daddy long legs’ or ‘mosquito hawks’) are flies belonging to the Tipulidae family. These large, fragile insects emerge in late summer and fall, but they only stick around for a few days. This is because the adult crane fly is very short-lived, only surviving for a day or two. They live only long enough to mate, lay eggs and bug people, before dying off. Many species of crane flies don’t even eat, though some may sip water or nectar from flowers.
Crane flies spend most of their life cycle underground. Adult females will typically lay eggs within 24 hours of emerging, and usually deposit their eggs around 1cm beneath the surface of the soil. Once hatched, the larvae live underground, feasting on the roots and crowns of turf, before pupating for the winter. Finally, the adult flies emerge from the pupae in late summer to begin the life cycle again.
Are crane flies dangerous to people?
Crane flies are often considered a nuisance, especially when they come indoors, but they are not dangerous to people or animals. Their long, spindly legs may make them look like mosquitoes, but crane flies don’t bite, sting or spread diseases.
Can crane flies damage my home?
Crane flies will not damage your home or any of your furnishings. They do not lay eggs indoors, and they won’t chew on wood or fabric.
Can crane flies damage my lawn?
The only area where crane flies have the potential to cause damage is outdoors. Adult crane flies lay their eggs in turfgrass, and their larvae feed on the root hairs, roots and crowns of the turf. This can cause damage to your lawn, resulting in yellow spots and bald patches. Other pests like skunks and starlings can cause secondary damage to your lawn by digging or pecking at turf to get at the larvae beneath the surface.
Fortunately, crane fly larvae are usually only a problem if they’re present in large numbers, and are more commonly a pest of golf courses.
Crane fly larvae control
If there are large numbers of crane flies in your area, you may have to implement control measures to keep your lawn healthy.
Keep your lawn neat and dry
Keeping your lawn neat and trimmed will reduce the likelihood of crane flies laying their eggs in your turf. Crane flies also prefer to lay their eggs in a moist environment, so keeping your lawn as dry as possible will help to discourage them. Avoid over-watering your lawn and provide better drainage in sites that are chronically damp.
Use biological control methods
If your preventative efforts have failed and your lawn is full of larvae, the best thing you can do is try to reduce their numbers. This will stop them from causing too much damage to your turf, and can also discourage other critters (like birds) from pecking your lawn to pieces.
Biological control methods are the most eco-friendly way to do this, as they don’t involve the use of potentially harmful chemicals. Introducing parasitic nematodes (like Steinernema feltiae) to your lawn can be especially effective, and may reduce larvae numbers by up to 50%.
Adult crane fly control
Adult crane flies can be irritating, especially when they come indoors. However, they are not dangerous, won’t damage your possessions and will drop dead of their own accord after a few days, so control methods usually aren’t necessary. If you want to stop them from getting into your house, install bug screens over your windows and keep your doors closed as much as possible.
If you really want to reduce the number of crane flies in your backyard, these bugs have several natural enemies (including bats, birds, frogs, yellow jackets and beetles) which can be encouraged into your garden.
If all else fails…
Chemical control methods can be used to effectively reduce the number of crane flies and crane fly larvae in your lawn, but these measures should be used with extreme caution. Chemical insecticides are often harmful to the environment and may affect non-target species, such as bees and other insects. They may also be harmful to people and pets.
Crane flies are a nuisance, but they aren’t at all dangerous and don’t bite, sting or spread diseases. Although they often come indoors, they won’t damage your property or any of your furniture, books or clothing. However, their larvae can cause damage to your lawn if they are present in large numbers.
You can reduce the likelihood of crane fly damage by keeping your lawn as dry as possible, especially around crane fly mating season (which is usually in August and September). Encouraging natural predators (such as birds, bats, frogs and beetles) into your backyard can also help to reduce their numbers.