The adult of a European crane fly resembles a large mosquito and can be from 1.5-2.5cm in length with a grey/brown body. The adults don’t bite and aren’t damaging to the lawn. The larvae on the other hand, also referred to as “leatherjackets” can be detrimental in large quantities as they can chew the grass down to bare soil. Leatherjackets are a greyish-brown colour and can range in size from 0.5-4cm in length, at maturity. Damage begins with yellow spots to bare patches of soil that are most visible from May to June. Secondary damage can also occur from skunks digging at your lawn to bring leatherjackets to the surface or birds pecking at them.
The best defence against a European crane fly is a healthy lawn. If your lawn is fertilized regularly, mowed accurately and irrigated properly it will be able to withstand insect feeding. First and foremost, watering deeply but less frequently will allow the roots of your grass to deepen and your lawn will be able to grow new leaf blades as well as repair itself quickly from any insect feeding. One inch of water once a week between 4am to 7am is crucial to maintain active growth. Proper mowing is also very important, you should never cut more than 1/3 of the grass blade off at any time to avoid shocking the grass plant. Keep your lawn around 3” long to make sure your grass doesn’t start using its food reserves, which will impact how quickly it recovers.