If the damage is extensive, the most effective time to treat a lawn for crane flies is the mid-to-late Fall in the Pacific Northwest. The best way to deal with crane flies and limit the effects of pesticides in the environment is to have a healthy lawn that can tolerate a certain amount of crane fly damage, but attract natural predators, such as robins and starlings. This can be accomplished by using a few techniques such as proper soil amendment, the proper grass type, and watering. You can download a PDF covering these methods here: Practical Lawn Care for Western Oregon
Here is a file on the crane fly in general from an Oregon State University entomologist: Crane Fly Damage in Lawns
It seems easier to contact a spray contractor to take care of problems as they arise, especially with a pest that seems omnipresent and just a little bit creepy such as the crane fly, but it is less expensive and more satisfying to take the situation in hand and prevent the problem by proper planting and management. The birds will thank you, too!
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