Crane flies are long, slender insects. They are usually brown or gray in color. They have very long legs and many people mistake them for mosquitoes. Homeowners often get frightened when crane flies gather on the sides of the house in large numbers.
In fact, crane flies do not bite or sting. Even if they manage to get into the house, they do not cause any damage. The damage might come in a month or so. The crane flies are probably there to deposit eggs in the grass. When the eggs hatch, the crane fly larvae will appear.
Many people call these creatures “leatherjackets”. Some people think this may be because they have thick skin. Some species of crane fly larvae are aquatic. They live in the water. Some species of crane fly larvae develop in damp soil. A few species, like the European crane fly and the giant common crane fly, actually damage turf grass. These insects cause so much damage that they are considered pests.
The adult crane flies deposit their eggs on the grass or on the soil. When the eggs hatch, the larvae burrow into the ground. They eat the root hairs, the roots, and the crowns of the grass plants. At night, the larvae sometimes come out of the ground and eat the grass stems and leaves.
Golf course greens keepers report damage to the greens from the crane fly larvae. They report that sometimes there is more damage caused by birds digging and pecking to get the larvae out of the ground.
Crane fly larvae cause the heaviest damage during the late spring. The larvae are largest at that time of the year. Many of them change into adults before fall so they can deposit their eggs before the weather turns cool.
During the late spring, homeowners might see cast-off pupal cases at the base of the grass. If the grass is tall, the skins may not be visible. There may be pale or yellow patches in the lawn. It may appear that white grubs have been attacking the grass.
Lifting a handful of pale or yellowed grass can reveal what is going on at the roots. If crane fly larvae or white grubs have been eating the roots, the grass can often be lifted up like a rug. The larvae will be visible on the soil under the grass.
Crane fly larvae are dark-colored insects. They may be grayish or a shade or brown. They often have black specks on their body. They can reach almost 10.5″ in length.
There is a measurement that experts use to decide when to treat turf pests. It is based on the number of insects per square foot. It is called the treatment threshold. The Extension Agent or a specialist at the garden store can tell what the treatment threshold is for turf pests in the local area.
Many people prefer to call a pest control professional to make the assessment of the lawn damage. These people can identify the pest and make the proper treatment when it will be most effective.