The Insidious Japanese Beetle

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July 9, 2015 at 4:56 pm

There are times you notice, when looking around your garden, that thing are a bit askew. What is it? You think for a moment and realize that there are holes in the leaves of all kinds of plants. Flowers, vegetables, trees – holes! What’s up?

Arriving on our shores from Japan in 1916, Japanese beetles are an invasive species that can do the damage described above to more than 200 kinds of plants that are known to be victims of this insidious insect pest. The list of plants that are attacked by Japanese beetles includes beans, strawberries, tomatoes, peppers, grapes, hops, roses, cherries, plums, pears, peaches, raspberries, blackberries, corn, peas, birch trees, linden trees, blueberries and countless others across the spectrum of species and genera of common garden plants.

Japanese Beetle Photo: University of Illinois Extension

Japanese Beetle
Photo: University of Illinois Extension

This time of year is when the Japanese beetle is most active and anybody growing plants in both a food or landscaping capacity should be on the lookout for them.

Japanese Beetle adults feeding on grapes leaves Photo: University of Illinois Extension

Japanese Beetle adults feeding on grapes leaves
Photo: University of Illinois Extension

The Japanese beetle is a roundish beetle approximately 1/3 inches long with a bright metallic green body and copper shell like wings. In its larval form they are white grubs, curled in a “C,” that feed on the roots of lawn grasses. They take on a grayish cast from the accumulation of soil and fecal matter in the hindgut and “V”-shaped pattern of spines on the underside tip of the abdomen.

Japanese Beetle Larva Photo: University of Illinois Extension

Japanese Beetle Larva
Photo: University of Illinois Extension

According to the University of Illinois Extension:

The Japanese beetle has a one year life cycle, spending about 10 months as a grub in the soil. In late June, the first adults emerge with most present in July and August. Some may still be found in early September. Throughout the summer, adult beetles feed on a wide range of plants and deposit eggs in the soil. Eggs hatch about two weeks later and grubs feed on decaying matter and roots until temperatures cool in the fall. They move downward and overwinter as a partially grown grub and resume some feeding activity in spring. Pupation occurs in late spring and adults begin emerging in late June.

Japanese Beetle adults feeding on corn silks Photo: University of Illinois Extension

Japanese Beetle adults feeding on corn silks
Photo: University of Illinois Extension

 

As stated above the Japanese beetle chews leaves of many plants and can even completely skeletonize the leaves. It also will eat corn silks and corn ear tips.

Controlling the Japanese beetle can be done with many common pesticides but those who want to do thing in a more sustainable way have several options. If the infestation is not too great then one can just pick the beetles off of the plants and put them in soapy water or vinegar to kill them. Keep in mind if you have anger in your heart and want to squash the beetles, they do give off a weird smell when squished. If the infestation is getting beyond the control of your picking hand then you may have to resort to floating row covers. Kaolin sprays are effective as a barrier as well.

Floating Row Cover  Photo: Johnny's Seeds

Floating Row Cover
Photo: Johnny’s Seeds

If you have suffered an infestation and want to get ahead of the Japanese beetle next year the bacterium, Bacillus popilliae, sold as milky spore powder (several brands are out there), can be applied to the soil. In its larval stage the Japanese beetle is susceptible milky spore disease caused by the bacteria and the USDA developed the bacterial application as a preventative measure.

One thing that you do not want to do though is set up what are called Japanese Beetle Traps. The traps do attract beetles, usually through pheromones, but they will attract many more beetles than will be trapped. More than likely, the traps will attract many more beetles than would have been attracted to your back yard by your garden plants in the first place!

parts of the country where the Japanese beetle has been found. Photo www.pioneer.com

Parts of the country where the Japanese beetle has been found.
Photo: www.pioneer.com

 

 

For further information on the Japanese beetle:

Wikipedia article on the Japanese beetle

University of Illinois Extension article on the Japanese beetle

University of Illinois Extension Specialist, Integrated Pest Management pdf on the Japanese beetle

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