What to do? (Treatment)
Some treatment options for you. Please also contact your local
Master Gardener for advice.
A healthy lawn will easily recover, even when the population
of leatherjackets is high. Watch weeds if sparse patches appear
and reseed if necessary.
Leatherjacket populations can decrease as much as 50% during
winter months and between March and May because of predators
and natural causes.
Cultural Management of Crane Flies
Grow lawns where lawns do best. Only establish turf in sunny
locations. Shade can reduce vigor and promote the survival of
crane fly larvae. In areas of low sun, consider a turf alternative
Remove excess thatch. Thatch is that layer of old dead grass
stems that builds up and reduces the availability of nutrients
and water if it gets too thick. Having thatch is good but too
much provides a nice environment for crane fly larvae. In fact,
just below the thatch is where you can find most crane fly larvae
Aerification cuts and brings to the surface soil and root cores
that then reintroduces oxygen into the soil, which results in
stimulating root development. Aerification also improves the
movement of water and nutrients into the soil.
Mow your lawn regularly. The correct mowing height is a function
of the type of grass species in your lawn. During the summer,
mowing every week or so is needed, as you never want to remove
more than 1/3 of the total grass blade length. Waiting longer
between mowing and removing more of the grass blade weakens
the grass. When you mow, leave the grass clippings on the lawn,
as they provide a safe source of recycled nutrients and thereby
reduce the need to additional fertilizer.
Lawns do need some fertilization, although not as much as is
sometimes applied. Mulching your cut grass clippings directly
on the turf also reduces this need as well.
Let your lawn go dormant during the dry months. Crane flies
are actually semi-aquatic insects and enjoy a moist environment.
Dry soil conditions in late summer and early fall may increase
crane fly mortality.
If watering is required, it should de done infrequently but
sufficiently long enough duration so to wet the entire root
zone. This means applying about one to 11/2 inches of water
every four to six days and nothing in-between. These infrequent
but deep waterings build deep and strong root systems that tolerate
crane fly damage.
Keep your lawn well drained. In areas where the soil is saturated
by water most of the time, consider planting something other
Biological Control of Crane Flies
Encourage birds to visit your yard, especially in the winter
and spring months. Bird predation can reduce a heavy population
of crane flies to just a few larvae in a short time.
Reduce the amount and frequency of all pesticides (herbicides,
fungicides and insecticides) in your yard. Predaceous ground
beetles feed on crane fly larvae (along with many other pests
Chemical Management of Crane Flies
If you've sampled your lawn and know that you're one of the
few with an actual crane fly problem, you may decide to arm
yourself with a pesticide. Be sure the chemical is legal for
home use on
lawns. Information regarding chemical treatment of crane fly
can be found on the WSU
Hortsense. Follow use, storage, and
disposal directions on the label. It's the law.