of Rhode Island GreenShare Factsheets
Insects on Lawns
One of the first steps in conducting an Integrated Pest
Management (IPM) program is to monitor the activity of weeds,
diseases, and insects regularly. For lawns in the Northeast,
monitoring every two to three weeks throughout the growing season
should be sufficient for detecting most insect populations. The
purpose of this fact sheet is to describe some techniques which
can be used to monitor insects.
The grubs of Japanese Beetles and their relatives (European
chafers, Asiatic garden beetles, oriental beetles) are active
in the soil during April and May and again from early August
through October. The grubs are cream-colored and normally C-shaped,
with a brown head and three pairs of legs. The easiest way to
sample for grubs is to dig a square about 6 inches on a side
and about 4 to 6 inches deep. Flip the sod upside down onto a
flat surface (a plywood sheet does nicely). Use a hand trowel
to break up clumps of soil in the ground or attached to the roots.
Remove any grubs you find and put them in a plastic cup to count
after you have finished. Be sure to beat the soil and roots on
the bottom of the sod with the edge of the trowel. Many grubs
will congregate in the thick roots just below the thatch, or
will be just in the thatch, near the soil line. In the spring
(April and May) and again in autumn (September and October),
the grubs will be at least 1/2 inch long and very easy to find.
In late July and early August, they will be much smaller and
very close to the root-thatch interface, so you must look very
carefully. Normally a healthy turf should be able to tolerate
at least 8 to 10 grubs per square foot without visible weakening.
If there are other stresses (such as drought, heavy traffic),
the turf may be weakened with as few as five grubs per square
foot. Note that some species of grubs are more aggressive or
damaging than others. As a general rule, European chafers cause
more damage than other species and so the tolerance level will
be slightly lower.
Chinch bugs are small, relatively soft-bodied insects which
remain active in the thatchy area just above the crowns of the
turf plants. They are most easily monitored by using three of
four empty coffee cans which have had both ends removed to leave
an empty cylinder. Stick one end of the cylinder into the soil
down about 2 or 3 inches (you may have to pound the can in with
a mallet or soften the soil a little first by watering the area).
Fill the cylinder with water (if possible, use a garden hose
with moderate pressure) and wait about five minutes. The chinch
bugs will float to the surface of the water, where you can count
them. Chinch bugs are most active in sunny areas with some water
stress. Conduct your sampling at the edges of droughty patches.
Sampling should be conducted from mid June through the end of
Sod webworms are caterpillars which
reach an inch in length and feed on the blades of grass. Sod
webworms feed actively at night and are virtually impossible
to find during the daytime if you merely inspect the turf. However,
webworms can be irritated to the surface by using an "irritating
drench". Put one or two tablespoons of a dish detergent in two
gallons of water and pour this solution over an area roughly
two feet by two feet. The detergent solution irritates webworm
caterpillars to leave their burrows and come to the surface within
five minutes where they can be counted. Sample in July and August.
If you sample at mid-day on a hot, sunny day, rinse the area
with clear water after you have completed the drench test. Otherwise
the soapy solution might burn the turf.
Bluegrass billbugs can cause serious
damage to lawns, particularly those which are predominantly
bluegrass. However, they occur
sporadically in New England. The easiest way to sample for billbugs
is to walk along the driveway or sidewalk on a warm, sunny day
in late May to mid June. Bend over and observe insect activity
on the pavement. Bluegrass billbug adults are black beetles with
very elongated "snouts". The total body length is about 1/4 to
3/8 inch (6-9 mm) and the tail end is somewhat pointed. If you
find an average of more that two billbugs for each minute of
your search, the likelihood exists that those adults will produce
enough offspring in the coming month to cause visible damage
to the turf. In addition, billbug larvae deposit fecal matter
which looks very much like sawdust into the thatch. If a finger
inspection of the turf reveals sawdust-like material, this serves
as a strong indication that billbug larvae are present. Usually
the larvae themselves will be found in the lower part of the
thatch. Inspect the area in a manner similar to that described
for white grubs. Larvae are active from late June through August.
Othe insects will be observed during your inspections.
Keep in mind that many of these are actively beneficial, either
by feeding on some of the pest species or by playing a significant
role in the breakdown of organic matter in the food chain. One
of the most commonly observed insects in a lawn is the ground
beetle. Actually, there are many species of ground beetles, each
of which is an active predator on a variety of soft bodied insects.
One of the most common species is about 1/4 to 3/8 inch (6-9
mm) long, somewhat broad and flattened, with a very shiny coppery
color. This insect moves rapidly along the surface of the turf,
especially on sunny days.
Adapted from the University
of Massachusetts Extension, 1999
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
of Rhode Island Cooperative Extension provides equal program