Here are some simple guidelines for monitoring crane fly populations,
all you need is a cutting utensil, ruler and a handlens.
What To Sample:
Larvae, or leatherjackets, are the damaging stage of the crane
fly's life cycle. You will be looking for grub-like tubular
worms. These larvae come in many different sizes depending on
the time of year you sample for them.
When To Sample:
Sampling can begin as early as January, however during some
years the larvae are small and difficult to see. In February
and March, larvae increase in size and become more apparent.
Where to Sample:
Select four areas in your lawn, these can be randomly made or
you can look for suspicious signs of damage. If you choose to
look at damaged areas, sample on the margins of the damage;
don't sample bare ground. Another good clue for finding suspicious
areas to sample, look for birds, especially robins, starlings,
and gulls. Many times I have found crane flies by looking for
holes punched through the grass by bird beaks. Birds are excellent
crane fly scouts.
How to Sample:
Once you've located your site, get your handy ruler out and
measure a six inch by six inch square.
Using a knife or cutting implement (I prefer using a butter
knife so I don't stab myself by accident), score the area by
cutting into the ground about 3 inches deep (just deep enough
to cut through the dense root mass).
Pull back the turf sample. Grass is usually tough and will hold
First inspect the hole in the turf for any larvae. Sometimes
they are feeding in the zone where the roots pull away from
the soil, these larvae will spill out as you pull up the sample.
Then inspect the edges of your sample; many times you will cut
into the larva. If you do this enough, you will become an expert
on how to determine the difference between sliced earthworms
Begin to break up the sample; many times the clod will tear
along areas where there are crane flies. Look for larvae in
the thatch layer of the turf, this is where most larvae prefer
to hang out and feed, about ½ inch deep.
Count all the larvae you've seen.
Multiple this number by 4 to determine the number of crane flies
per square foot of lawn.
Replant your sample back into the divot that was created. Turf
is hardy and will reestablish with no problems and it will become
Repeat this three more times to find the average number of crane
flies per square foot of lawn.
Now that you have a good idea how many crane flies you have
in your lawn, read on and make an educatued decision about what