Ask The Master – How To Get Rid of Japanese Beetles

Throughout history, beetles have represented everything from the immortal Egyptian Sun God Khepri, to Ladybirds, to a killer of forests, to rolling a ball of dung around as its home. Its ability to emerge annually from underground or from inside of a ball of manure is indeed impressive. To those who watch detested Japanese Beetles come alive every July to decimate favorite flowers and fruit crops, they may seem immortal!

Having been introduced from Japan into New Jersey in 1916, they immediately took advantage of the average homeowner’s love of a mowed lawn. Since there were very few native predators to contend with, and preferring moderate temperatures and moisture, Japanese Beetles began spreading prolifically throughout eastern Canada and the United States.

Their grubs are responsible for dead patches of lawn during the summer because they live under the surface of the sod, going deeper in the winter, but moving to the roots of your grass in spring to eat till time to emerge in June and July.  Then they spend months making lacework of your roses, berry bushes, trees and shrubs. In late June and early July, each female will lay 40-60 eggs in lawns, ready to emerge in even greater numbers the following June.

Today they are one of the most reviled of landscape pests. So, Japanese Beetles are here to stay. You can battle with them plant to plant, protecting only your finest specimens, or go on an annual full scale attack to drastically reduce their numbers in your lawn over time.

While they are able to fly distances of a mile or more, they generally remain close to where they spend the winter, especially if it’s a mowed area.  

Whether you choose to use chemicals which can possibly do more harm than good, or choose to be more hands on with traps and natural predators that have tasted both the grubs and the beetles and found them to their liking, you can take action to reduce their numbers in your specific area. Usually a mixture of all methods, carefully selected for a specific purpose, can be your answer.

There’s nothing like trapping a bag full of Japanese Beetles, knowing that they will never lay another egg, for garden pest gratification.  Place several traps at a 30-40 foot distance from your gardens and landscape plants on the downwind side. You want the scent to bring them to the traps and not your plants.  Possibly speak to neighbors about doing the same thing to better cover a larger area. Since Japanese Beetles feed in groups, a little bit of overkill will go a long way.

Properly applied, a natural preventive is Milky Spore which is slightly costly, but which continues to provide a disease to the grubs to kill those parents which escaped the traps or your own hands. It is completely safe for mammals.  Also beneficial nematodes will destroy grubs in the same way.

When selecting plants for your landscape, beetle resistant species are available and may help reduce the numbers by providing plants that they will not feed on. 

Keep fruit crops picked as they ripen and give off scents which attract other beetles.  Trap or destroy beetles as early as possible so they don’t “invite” other beetles to a lunch date.

Row covers on garden crops will keep all beetles from reaching them.  For highly prized landscape plants such as roses, cover the entire plant in the evening with a cheesecloth to trap those already in the debris under the plant and to keep new beetles from landing. Check early in the morning and drop pests into soapy water.

Be very active in your landscape and garden in the late morning and early afternoon in order to stay ahead of Japanese Beetles.  Finding them quickly and often will keep them from multiplying. Take a bucket of warm soapy water to the garden with you. Use a small plastic container containing some soapy water to go from plant to plant. Starting at the bottom, carefully knock beetles from the plant into the container which you can then dump into the larger bucket.

If you are able to keep farm fowl, they love beetles of all sorts. Feed wild birds in the fall and winter to encourage them to stay in your area during the summer. Remove feeders in the spring to encourage them to eat their natural food sources which would include beetles.. 

You may not be able to completely eradicate Japanese Beetles in your landscape but you can make them much less destructive.  Call your Master Gardeners for additional help.

Certified Master Gardeners are local volunteers trained by Penn State to answer Horticulture questions with properly researched information. For a “best practices” answer to your question, call Penn State Jefferson County Extension at 849-7361, Ext 508, e-mail JeffersonMG@psu.edu, or mail your question to 186 Main Street, Suite 3, Brookville, PA 15825.  

Penn State is an equal opportunity, affirmative action employer, and is committed to providing employment opportunities to all qualified applicants without regard to race, color, religion, age, sex, sexual orientation, gender identity, national origin, disability or protected veteran status.

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