FEATURESTORY
by Mike McGroarty
How to Get Rid of Japanese Beetles and
Grubs in Your Lawn
F
irst, it’s important to make the connection
that the white grubs in your lawn will hatch
into Japanese Beetles and if you have Japa-
nese Beetles they will lay eggs in your lawn
that turn into white grubs. Japanese Beetles can se-
verely damage your roses and other plants in your
landscape because they feed on the leaves and can
almost completely defoliate some plants.
The white grubs ruin your lawn. They feed on
the roots of the grass near the soil surface. The dam-
age usually shows up when it’s hot and dry because
without a good root system the grasses in your lawn
will start dying. Damaged areas in your lawn feel
spongy when you walk on the grass because of the
tunneling that’s taking place under the surface. If the
damage is extensive the grass can be pulled up like
carpet because the roots have been chewed off.
Skunks, crows, grubs and other critters dig up
your lawn to get at the grubs. In the fall when skunks
are instinctively packing away the food to fatten up
for the winter they can destroy a lawn in one night if
it has a heavy grub infestation. Look for little holes in
your flower beds because that usually means that the
birds have been digging for grubs.
During the summer months when the soil is
warm the grubs are usually at a depth of 2″ or
less. As winter approaches they go deeper into the
soil and become almost inactive. As soon as spring
arrives and the soil temperatures increase they move
back toward the surface and start feeding on the
roots of your lawn once again. They eat away for
another 4 to 6 weeks, then emerge from the soil as
adult Japanese Beetles and start feeding on your
landscape. As they devour your landscape they start
laying batches of eggs, usually 20 to 60 eggs total per
female beetle. And the life cycle starts all over again.
You can lift areas of sod in your lawn where you
suspect you might have white grub infestation and
look for the grubs. They are white in color and range
in size from 1/2″ to 1″ long. If you have more than 6
grubs per square foot it’s time to think about a way
to control them. If you opt for a chemical control
there are several products on the market and the best
time to apply them is late August and early Septem-
ber. The white grubs are much easier to control when
they are smaller and closer to the surface of the soil.
June 2018
Biological control of white Japanese Beetle grubs
can be achieved by applying the insect parasitic
nematode species Heterorhabditis bacteriophora. You
can purchase these nematodes under a variety of
different trade names. Another biological control is
Milky Spore which is actually bacterium pacenibacil-
lus popillae. However, this is a long term approach
and can take years for the spore to spread through-
out your lawn. It actually requires the grubs to ingest
the spores and then as they die their carcass becomes
part of the control to help spread the spores through-
out your lawn.
Japanese Beetle Traps
Do they work work? Well, the jury is still
out. Most traps use both a sex lure that attracts male
beetles and sweet smelling lure that attract both
sexes. Without a doubt these traps attract a lot of
beetles, but some research indicates that they attract
more beetles to the area of the trap than they actu-
ally trap. That means that plants in the path of the
trap might suffer more damage. If you use traps place
them near the edge of the property and well away
from plants that are damaged by Japanese Beetles.
Since there is some biological control that natu-
rally takes place without your intervention it is rec-
ommended that you only consider chemical control
when the infestation is severe because the chemicals
disrupt the natural process of control. GG
Mike McGroarty is the owner of McGroarty Enterprises and the
author of several books. You can visit his website at Freeplants.
com and read his blog at Mikesbackyardnursery.com.
www.GardenandGreenhouse.net
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