Franklin County Horticulture
Fasten your seatbelts as Japanese beetles arrive
July
1, 2001
Japanese beetles are here!
Gardeners,
start your squishing! The dreaded
Japanese beetles are flying and coming to a town near you!
Japanese
beetles are now showing up in Franklin County. Several phone calls and
eyewitness reports indicate that these beetles are all over the county. We
just started seeing them around the 21st of June, so it’s hard to
predict how bad they will be this year.
The adult Japanese beetle is a serious pest of many garden and ornamental plants, mainly because it can never satisfy its appetite. The immature or “baby beetles” are grubs which love to feed on your lawn roots.
For
best control, choose plants that are not as tasty to the Japanese beetles.
These plants include boxelder, red and silver maples, boxwood, dogwood,
euonymus, white and green ash, hollies, magnolias, red mulberry, common lilac,
and most evergreens. Some plants, such as the oaks, may have occasional
feeding damage.
Control
Methods
Hand
picking and exclusion:
Hand picking is the most effective manner of control. One of the easiest ways to remove beetles from small plants is to shake them off early in the morning when the insects are sluggish.
Since we are big UK football fans, we always have large beverage cups around. Go out early in the morning after filling the cup with soapy water. Then, shake the beetles into the cup. Plants that are of great value to you should be covered with cheesecloth or other fine netting during peak beetle activity.
Hand
picking works well for smaller plants and when beetle numbers are relatively
low. And yes, it’s true, large groups of beetles attract more beetles. The
newcomers figure that by seeing other clusters of beetles, it must be a good
place to stop for lunch! So,
removal of Japanese beetles from plants as soon as you see the beetles will
help reduce “tourists.”
Insecticides:
Several
insecticides are available for the control of Japanese beetles. If any of you
have some insecticidal soap left over from the tent caterpillar war, this
product will also work on Japanese beetles. However, the same application
tricks apply. For this product, contact must be made directly with the insect
to kill it.
Sevin is also recommended for control of adult Japanese beetles. However, this product is toxic to honeybees. For best results, apply this product at dusk, after the honeybees have returned to their nests.
Foliage
and flowers should be thoroughly treated. Applications may need to be repeated
at 7‑10 day intervals to prevent reinfestation during the adult flight
period, or after heavy rains. Follow label directions and avoid spraying under
windy conditions.
Cultural
controls:
Eliminating
the watering of the lawn can also help control of Japanese beetles. Japanese
beetles lay their eggs in the soil, and moisture is required for the eggs to
hatch. If water is not available, the eggs will not hatch. So, although a brown
lawn may not be much to look at, it will prevent grub problems. If the immature
Japanese beetle does not live, then there will be no adult Japanese beetles.
Frequent irrigation in June and July may attract egg‑laying female beetles to the turf, especially if surrounding areas are dry. High soil moisture also increases egg survival. If lawns are irrigated during June and July, be on the lookout for signs of grubs later in the summer.
Conversely,
adequate soil moisture in August and September (when grubs are actively feeding)
can help to hide root injury. Irrigated turf can sometimes tolerate 20 or more
grubs per square foot before showing signs of injury.
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