Barb I; Barrie, Ontario asks: Our lawn care company said we should have our lawn sprayed for "leatherjackets" which look like very very large mosquitos. What are they and what can we buy to treat them ourselves?
Dear Barb: Leatherjackets are the larvae of Crane flies. It's the Crane fly that looks like a large, daddy-long-leg type of mosquito, but they do not sting, nor do they cause any damage to our lawns. The leatherjacket is the Crane fly larva. It gets its name from its leatherly-looking skin.
There are several signs that indicate the presence of leatherjackets such as large numbers of adult Crane flies in late summer. Grass growth slows and yellow patches appear. Grass is easily pulled up with little or no root system. Starlings peck at the grass in an attempt to eat the grubs.
Leatherjackets feed on the roots and stems of grass plants at or below ground level. Feeding on the grass roots continues through the fall and into the following spring as the larvae grow.
The only insecticide I could find that specifically list leatherjackets on the label is manufactured by Bayer and is called Provado Lawn Grub Killer. The product contains Imidacloprid, which is deadly to bees. Merit Granular Insecticide lists control of crane flies which are the adults of the leatherjackets. Merit will work faster than the Provado.
There are various non-insecticide measures you can take to control leatherjackets using nematodes. Various web sites sell nematode products specifically designed to attack leatherjackets. It's environmentally more correct, but the control is slower and depends heavily upon proper watering.