This means war: Japanese beetles keep her hopping
Let’s keep our fingers crossed. Last year, I saw few Japanese beetles and that was great. The previous summer, I needed to make the rounds in the garden several times a day with a jar of soapy water and a rubber glove, bent on genocide.
These pests have a predictable lifestyle, emerging from the ground in mid-June to begin an intense six weeks of activity in our farms and gardens. Some diehards will stay around until September, but most of them have completed their life’s work in August.
The adult beetle is rather attractive, less than half an inch long and metallic green with copper-brown wing covers. Small white tufts on each side distinguish them from other similarly colored insects.
Japanese beetles feed on more than 300 varieties of plants, including roses, raspberries, blueberries and other small fruits, including grape vines. They have a particular liking for my Japanese ornamental cherry tree, which must remind them of home, and I am told they also enjoy feasting on poison ivy.
They favor sites in direct sun and usually a group of them will descend in the same area, land on the top of a plant and work their way downward. They feed on flower petals and between the veins on leaves, leaving the foliage skeletonized.
The adults spend their time eating and mating, and lay batches of 40 to 60 eggs in damp, grassy spots. Excessively dry weather will kill eggs and larvae, which probably accounts for their rarity last year in an unusually dry summer.
The newly hatched grubs are cream colored with brown heads, and they stay in the soil feeding on roots until cool fall weather causes them to hibernate.
After a winter sleep, the grubs begin to feed again, pupate in June and then emerge from the ground as adults to begin the cycle all over again.
Management is difficult.
There is a great sense of satisfaction and revenge for the gardener in removing a full bag of dead and dying beetles, but we are told most of these bugs were attracted to our area from up to a mile away, lured by the pheronomes in the traps.
Hand-picking is the most effective measure but is time-consuming. These are insecticides such as pyrethin, rotenone, neem, methoxychlor, malathion and carbyril (Sevin), which are deadly to these beetles, but also kill beneficial insects. I am reluctant to resort to them out of concern for bees, butterflies and other pollinators.
The best time to attempt to control grubs is while they are feeding in late April until early May, and again during August. Diazinon or Oftanol can be sprayed on and watered into the grassy areas where they are feeding underground.
A direct spray or insecticidal soap will kill beetles on contact, but does not prevent subsequent attacks.
New beetles are apt to arrive on clear days when the temperature is between 85 and 90 degrees and winds less that 12 miles per hour.
Another means of attack is milky spore, a naturally occuring bacteria that provides long-lasting control of the grubs. It is best applied in early fall and, once it takes hold in the soil, it will spread naturally to untreated areas.
If we have a bad year this time around, I plan to put a trap on the fence across the road and also begin hand-picking.
Then, in case of a really uncontrollable invasion, I will ready my puffer full of Sevin powder as a last resort. But, here’s hoping for the best.
Janet Del Turco is a local gardener and a graduate of the Ohio State University Master Gardener program.
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