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Japanese beetles

With a metallic-looking green color behind their heads and a metallic brown abdomen, Japanese beetles appear kind of attractive, but they can be pests.

Kathleen Cue can tell you that Japanese beetles are pretty.

The area behind their heads is a metallic-looking green. Their abdomens are metallic brown in color.

But gardeners might not appreciate these bugs so much.

“At this time of the year, they are absolutely adoring our fruits that are ripening,” said Cue, the Nebraska Extension Horticulture Educator for Dodge County.

It’s not unusual to find these bugs on raspberries and peaches.

“I’ve had peaches brought in that were so covered in Japanese beetles that I couldn’t tell it was a peach underneath it. That’s a lot of Japanese beetles,” she said.

And when it comes to food, these bugs have a broad palate.

“There’s over 300 things that they’ll feed on,” she said.

With them liking so many things, they are harder to manage.

These insects start appearing in June and many people know that Japanese beetles lay eggs in the soil and hatch out as grubs.

“So their thought is if they kill all the Japanese beetle grubs in their soil, they won’t have any problem with them on their Linden tree or their grapevines – and that’s not the case,” she said.

That’s because there are lots of areas where the soil never gets treated for Japanese beetle grubs — in ditches, along fence lines and in untreated lawns.

“So all of those areas will still be sending out adult beetles at some point,” Cue said. “And the beetles will always gravitate toward their favorite foods — Lindens, roses and grapevines.”

If folks are spending the money to manage Japanese beetle grubs for the lawn’s sake, that makes sense, she said.

“But if they’re spending the money to manage Japanese beetle grubs for their trees or shrubs’ sake, then that doesn’t make sense to do that, because they’ll always fly in from other locations,” she said.

Those who want to keep the Japanese beetles’ eating damage to a minimum may want to treat their plants — in June.

Cue offers a word of caution regarding a systemic insecticide.

“Nationally, it’s illegal to use a systemic insecticide on any trees,” she said.

A systemic insecticide doesn’t just sit on the outside of a plant’s leaves, twigs or trunk. Instead, it becomes absorbed into the tissues and becomes part of the tree.

It’s illegal to use a systemic insecticide on trees is because these products also can be translocated (moved) to flowering plants.

“If there’s a pollinator that comes along and feeds on the nectar of that flower, it will die,” she said. “If you have a bumblebee that feeds on the flower of a Linden tree and it’s been treated with a systemic, then it (the bee) dies. And our pollinators are in trouble.”

Bees pollinate flowers and human food crops and experts estimate a third of the food eaten daily relies on pollination mainly by bees. But there has been a decline in pollinators due to various causes including loss of habitat, improper use of pesticides, poor nutrition and disease.

However, people can apply an insecticide that coats the leaves but is not pulled into the tissues, so when the bugs eat on the leaves they die.

Cue said the most prevalent of these insecticides is Chlorantraniliprole. This topical spray has little to no impact on pollinators but is very effective against Japanese beetles.

A tree service will be needed to apply this insecticide.

“That isn’t something that’s available to someone to just purchase,” she said.

But Cue said the time to treat trees with this chemical is in June.

Japanese beetles are scaling back on how much they’re feeding on trees and their preferred foods seem to be fruit right now.

“And in those cases, you don’t really want to apply an insecticide, because you’re talking about eating these at some point,” she said.

Here’s where a bucket of soapy water comes in handy.

When a plant with Japanese beetles is disturbed, their impulse is to drop straight to the ground.

“We can use that habit against them by putting our bucket of soapy water beneath them, tapping the branch and watching them all fall into the water and drown,” she said. “That way you get to eat more of your fruit than they do.”

For information about other insects and plants, contact Cue at: 1206 W. 23rd St., Fremont, NE 68025-2504; (402) 727-2775; or kcue2@unl.edu.

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News Editor

Tammy Real-McKeighan is news editor of the Fremont Tribune. She covers news, features, religion stories and writes the weekly faith-based, Spiritual Spinach column.

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