This foreign invader has destroyed U.S. vegetation since 1916 JAPANESE BEETLES

By Stephanie Hughes

OSU Extension master gardener volunteer

They are almost here!

We generally see these destructive insects around the 4th of July.

A better way to know the time of their arrival is by using the OSU Growing Degree Days Site at go.osu.edu/growingdegreeday. This site helps you know when they are about to emerge.

Why are they such a problem? Because they don’t belong here.

In 1916 in New Jersey, this insect was introduced from Japan. It has had major consequences on the woods, gardens, yards and all farmers and gardeners.

They have no natural enemies here, though starlings, crows, moles, shrews and skunks eat them.

The cycle begins as 40-60 eggs are laid in moist soil in July.

Then these white grubs feed on the roots of turf grasses, vegetables and seedlings.

October finds the grubs burrowing deep into the 60-degree soil to wait out winter.

As soil warms up to the 50s in spring, the grubs feed on roots, making large patches of dead sod, as the grass plants do not have enough roots to sustain themselves.

June to July is time to pupate, emergence as adults to eat, mate and reproduce.

As adults, they can eat leaves, flowers and overripe and wounded fruit.

They love grapes, roses, lindens, sassafras, Norway maple, Japanese maple and purple plum, along with other species.

They seldom feed alone, but in groups, emitting a smell that attracts others.

Thus, removing the first beetle without crushing it will reduce the chance for hundreds to come and eat your plants.

They love the sun, and feed on foliage in a sunny location.

Traps are unsuccessful and detrimental, as traps are baited with either a female pheromone – thus attracting males, and/or a tasty food type – thus attracting the beetles to anything along their flight paths.

To save lawns, the best action to take is to first identify the grubs as Japanese beetles, as there are other insect grubs that eat grass roots as well.

Once identified, application of insecticide at a specific time in the cycle is vital. Be sure to read and follow all label directions before using. The OSU Extension office can help with identification.

To reduce adults, pick them off plants and place them into a can of soapy water.

To learn about these insects, go to go.osu.edu/japanesebeetle.