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More About the Japanese Beetle

We posted about the Japanese beetle back in August but thought, since it is such a cool beetle and since it might be heading your way sometime in the future... that you might be interested in a bit more information.

Japanese Beetle, Popilla japonica

“The Japanese beetle is probably the most devastating pest of urban landscape plants in the eastern United States.”

~ M.F. Potter, D.A. Potter, and L.H. Townsend, Extension Entomologists, University of Kentucky College of Agriculture

Japanese beetle (native to Japan) likely arrived in the United States in 1912 in a shipment of iris bulbs. It was first found on PEI in 2009 in a campground between Charlottetown and Cornwall. It now can be found in some areas of Charlottetown and is likely in other locations as well.

The adult Japanese beetle feeds on the foliage and fruit of more than 300 plant species, including elm, maple, grape vine, peach, apple, apricot, cherry, plum, roses, zinnia, corn, asparagus, soybean, blueberries, raspberries, blackberries and other plants. The odors from the damaged leaves of certain plants seem to attract the beetles that then, aggregate and feed as a group, starting at the top of the plant and working their way down causing serious defoliation.

The larval stage of the Japanese beetle also causes damage. Adult beetles dig down 2—3 inches in the soil to lay their eggs. The eggs hatch and the larvae begin feeding on the roots of nearby plants. Adult beetles are attracted to moist areas, such as well watered turf or gardens, as their eggs and small larvae need adequate soil moisture to survive. The preferred food of larvae is turf/grass roots but they will feed on other vegetable and shrub roots as well. The feeding larvae reduce the plants ability to take up water, and can cause large brown patches to form anywhere turf is plentiful - your lawn, golf courses, parks or even a cemetery.

What can you do if you have the Japanese beetle?

There is no silver bullet... the Japanese beetle is not easy to control once you have it but you can do some things to minimize the damage it does and reduce its population numbers.

There are a few things to consider when managing Japanese beetle populations. It is important to recognize that both the adult beetle and the larvae (grubs) cause damage. Adults are capable of flying and will travel a considerable distance to feed on preferred host plants so controlling their population in your yard does not prevent re-infestation. Beetles attract beetles, so keeping the population low attracts fewer beetles to your yard.

Get rid of the beetles the minute you see them in the Spring. Controlling the beetle as soon as they emerge helps to keep the population down in your yard or the local area.

When replacing or adding new plants to your yard, select plants that the beetle tends to avoid (this does not mean that they will avoid them totally). Plants the beetles prefer are roses, grapes, lindens, Norway maple, Japanese maple, some flowering crab apples, fruit trees, horse chestnut and many others. Lists of preferred host plants and “resistant” plants can be found online.

Manually controlling a population in a small area by hand picking beetles or shaking the beetles off the plants into a bucket of soapy water, can be effective. Morning is a good time of day to do this as the beetles are sluggish because of the cooler temperatures.

If you have quite a large population of beetles, a small hand held vacuum can be used to vacuum the beetles off your plants. Empty the vacuum into a bucket of soapy water to get rid of the beetles. Warning - the vacuum may only be good for vacuuming beetles after that!

Excluding the beetles with materials such as cheesecloth or fine netting can protect highly prized plants.

Neem oil products can deter adult beetle feeding for 3-4 days. Insecticidal soap, extracts of garlic, hot pepper, orange peels and companion planting seem to be ineffective.

There are some products that can be applied to the soil to deter the larvae but since the larvae prefer to feed on the roots of turf, but will feed on other plant roots as well, they can be anywhere making application of these soil applied products problematic.

Good Luck!

- Beth Hoar, Chair, PEIISC

The life cycle of the Japanese beetle. Adult beetles and larval feeding damage plants… a double whammy! If you like entomological illustration… check out this website: http://www.entomologicalillustration.com/portfolio11JapaneseBeetleLifecycle.html
The life cycle of the Japanese beetle. Adult beetles and larval feeding damage plants… a double whammy! If you like entomological illustration… check out this website: http://www.entomologicalillustration.com/portfolio11JapaneseBeetleLifecycle.html