One of the most serious garden pests, Japanese beetles,
hits gardens in zone 5-6 in July and early August. Gardeners in warmer zones
may deal with them earlier. Most
gardeners have had to deal with this serious pest at one time or another. The first Japanese beetles were found in New
Jersey in 1916 and since then have spread west and south. They are as the name suggests, native to
Japan.
The Japanese beetle is a fat, oval, metallic bronze and
green beetle, with a row of white spots along the sides of the body. The spots
are clumps of white hairs. The immature
stage is a tan-white grub that is found in the soil of grassy areas where it
feeds on plant roots. It has a
distinctive v shaped row of bristles on its rear end. Japanese beetles can fly fairly well.
In Michigan, late June to early July is the time when
Japanese beetle damage on plant parts above ground first becomes apparent and
feeding continues for about a month.
However beetles emerging from the soil can continue into August and some
beetles may persist all summer. Feeding on the roots of turf grasses is
heaviest in the later part of summer and again in early spring.
When Japanese beetles emerge from the soil they eat for
a few days and then begin mating and the females begin laying eggs back in the
soil. In the afternoon she leaves the
plants she has been eating, goes to the ground and burrows up to 4 inches down
and lays a few eggs. This continues for
days until she has laid roughly 60 eggs.
In warm moist soil the eggs will hatch in about 10 days
and the new grubs begin feeding on grass roots. Eggs and small grubs are very susceptible to
drying out and not irrigating the lawn in summer may help control a grub
population.
Adult Japanese beetles will feed on over 300 species of
plants, including most of our ornamentals, trees, and fruits. They eat the tissue from between leaf veins,
turning them into ragged skeletons which brown and fall off. They may also eat soft fruit. The damage the grubs do in lawns and on golf
courses appears as yellow spots, where the turf can be rolled back in patches
like a rug.
As they feed and mate Japanese beetles release a scent
that attracts other Japanese beetles and populations in an area may soon
contain thousands of beetles. They can
do serious defoliation damage to plants, although the plants will generally
recover in late summer when feeding damage is less. It is estimated that damage and cost of
controlling Japanese beetles to Americans is over 450 million dollars each
year.
Control
in home landscapes
In July homeowners can apply grub control products
containing imidacloprid (Merit) and halofenozide. In spring if damage is apparent use grub
products containing trichlorfon (Dylox) and carbaryl (Sevin). Remember that these pesticides will harm many
kinds of animals in the soil and may have toxic effects on pets and children
too.
For ornamental plants a general insecticide for
ornamental plants can be used but once again these will kill many types of
insects, good and bad. Systemic products may do some good - but the beetle has
to eat part of the plant to be killed.
They are best used early, before beetle populations get high.
For fruit trees,
including ornamental types of fruit trees, a multipurpose orchard spray should
be used as directed on the label. For
vegetables use an insecticide approved for edible plants. Vegetables that don’t require pollination can
be covered with lightweight row cover material to exclude beetles.
Hand picking and using a hand vacuum to remove beetles
as soon as they are seen is helpful.
Once beetles get established they attract more beetles. Japanese beetle traps are on the market but
for them to work you must locate them far away from the plants you want to
protect.
Research published in the Journal of Economic
Entomology, 04/08/2009, found that a mixture of two essential oils, wintergreen
and ginger oil, was quite effective at repelling Japanese beetles. Peppermint oil was also a strong repellant.
(Coffee and citronella oils actually seemed to attract Japanese beetles). More research is being conducted to find the
best way to use these oils as beetle repellants on crops. These oils could be applied to food crops
safely and would be relatively benign to the environment.
Other research conducted at the USDA Application
Technology Research Unit in Wooster, Ohio found that geraniums could be part of
the war against Japanese beetles.
Entomologist Chris Ranger found that Japanese beetles that ate geranium
leaves were paralyzed within 30 minutes and stayed immobile for up to 24
hours. While immobilized they are easy
prey for birds and other predators or could be swept or vacuumed up.
Interestingly enough the paralytic effect of geranium
leaves on Japanese beetles has been known since the 1920’s, about the time the
pest arrived in the United States.
Ranger and a colleague have just begun to develop a natural pesticide
using geraniums and have applied for a patent.
Other
natural controls
Japanese beetle traps that attract the beetles and then
drown them have been around for years, but in small yards the placement of
traps can be a problem. The traps
attract more beetles than might normally be in the area and need to be placed a
good ways away from plants you want to protect.
A few years ago milky spore disease was introduced into
areas where Japanese beetles are found.
This fungal disease attacks the Japanese beetle’s immature stage- the
grub that resides in your lawn destroying grass roots. Milky spore disease is now found in stores
and garden supply catalogs for you to sprinkle over affected areas.
A new protozoan disease that also kills Japanese beetle
is being released throughout Michigan.
These natural controls are safe for the environment and kill only
Japanese beetles. Both
the milky spore disease and protozoan controls take many years to begin to be
effective in an area. But combining
those controls with faster acting repellents made from essential oils or a
geranium knock out spray could be the environmentally friendly solution
homeowners have been waiting for.
No comments:
Post a Comment