There
is hardly a gardener out there who hasn't encountered a Japanese beetle. The
adult Japanese beetle is a shiny, metallic green with copper-brown wing covers
and it’s about 3/8-inch in length. Not all metallic green or copper beetles are
Japanese Beetles To be sure of what you’re dealing with, you can look closely
at the underside of the beetle and you’ll also see 5 small, white tufts under
the wing covers and an additional tuft at the end of the abdomen.
Japanese beetle, (species Popillia
japonica), an insect that is was accidentally introduced into the United States
from Japan about 1916, probably as larvae in the soil around imported plants.
Japanese beetles are known to feed on more than 200 species of plants,
including a wide variety of trees, shrubs, grasses, and nursery plants. They
are gregarious insects, often feeding in large groups upon a single tree. A
swarm of Japanese beetles can denude a peach tree in 15 minutes, leaving
nothing but bare branches and the fruit pits. Keep in mind that the adult
Japanese beetles are only around for a little over a month, so don’t
automatically reach for the sprayer unless they become a serious problem. Some
years are better than others.
Efforts are being made to control the
spread of this pest. Poisonous sprays control the adult beetles but differ in
the length of their protection against re-infestation. Several of the beetle’s
natural enemies—species of parasitic wasps and flies that in Japan were found
to prey on the larvae—have been imported into the United States, where some of
them have become established. Of even greater promise as a biological control
is a disease-inducing bacterium, Bacillus popilliae, which causes milky disease
in larvae; its use has reduced Japanese beetle infestations in some areas.
Least Toxic Japanese Beetle Controls
There aren’t many natural controls for
adult Japanese beetles. Birds aren’t partial to them and although some
predatory wasps and flies have been imported, their population isn’t large
enough yet to control the Japanese beetle problem.
The most effective natural control is to
go into your garden with a jar of soapy water and knock the beetles into it.
Japanese beetles feed in groups, starting at the top of plants, so it’s
actually pretty easy to fill a jar with them.
Insecticidal soap will kill adult Japanese
beetles only if it is sprayed directly on the beetle. It does not have any
residual effect, meaning that beetles that aren’t sprayed directly won’t be
harmed.
A word of caution about the pheromone
beetle traps. They will attract beetles, but you’ll probably wind up with more
beetles coming into your yard than you would have without the trap. The
original intention of the traps was to track when and how many Japanese beetles
were in the area, not as a means of eradication.
Finally, if you have repeated intense
infestations, you should check your soil in late summer to see if you have a
large grub population. Lift a 1 sq. ft. section of turf. If there are more than
a dozen grubs in this small area, consider treating your lawn with some type of
grub control. However, not every garden that has a Japanese beetle problem is
associated with a lawn full of grubs. The beetles can hatch in your neighbors
lawn and find your tasty garden with very little effort.
More Toxic Controls, to be used with Extreme Caution
There are several insecticides labeled
for use on adult Japanese beetles, including:
Bayer Advanced Garden Multi-Insect
Killer Concentrate
Carbaryl (Sevin)
Neem extracts
Orthene
Ortho Bug-B-Gon Garden & Landscape
Insect Killer Concentrate
Orthene Turf, Tree & Ornamental
Insecticide
Spectracide® Bug Stop Multi-Purpose
Insect Control Concentrate
Spectracide® Triazicide® Soil & Turf
Insect Killer Concentrate
These sprays will kill on contact and
also have some residual effect. Keep in mind that these sprays will kill more
than just the Japanese beetles, so use them only for extreme infestations. You will want to avoid these products if you have a wildlife habitat of any kind! And
again, Japanese beetles are only a pest for a little over a month, so don’t
over react.
Always read and follow label directions
when using any pesticide and Good Luck!