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Unwelcome guests cozy up to gardens in Rock County

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Ryan Broege
June 22, 2012
— Like a burglar that helps himself to whatever's in the fridge, Japanese beetles are unwelcome guests making themselves comfortable in gardens across Rock County.

Japanese beetles have an appetite for more than 300 plant species and a biological imperative to skeletonize plant matter. They grow from a hardly conspicuous presence to an outright infestation in about three days. Once established, there's no easy way to get rid of them.


"A bug from hell," is how UW Extension entomologist Phillip Pellitteri characterized the critters.


In every state east of the Mississippi except Florida, Japanese beetles are an increasingly common sight during the summer months. They first showed up in the United States in New Jersey in 1916.


This year's unseasonably early spring means Japanese beetles are showing up early.


Pellitteri said he saw this year's first Japanese beetles 10 days ago, but nothing more than "trickles."


After the beetles converge on a garden, they release pheromones beckoning others to join them and begin mating.


UW Extension horticulture educator Mike Maddox described the mating beetles as a "wiggling, iridescent bordello," referencing bugs' distinct metallic green thoraxes.


Master gardener Kristine Zaballos tends to a kitchen garden, a vegetable garden and perennials. She's been battling Japanese beetles for years but said last year was easily the worst. Her raspberries and roses were hit the hardest.


"They can do damage so quickly, you can feel helpless," she said.


Maddox attested to the emotional toll Japanese beetles visit upon gardeners.


"They've really freaked people out," he said. "They can seem like a dominant presence when they're swarming in your garden."


Baited trap bags are ineffective because they only attract more of the pests, Maddox said.


Zaballos engages in hand-to-hand combat against the beetles. At dusk, she takes a bowl filled with vinegar to her garden and shakes the insects off of the leaves and stems and into the bowl. She chooses dusk because Japanese beetles will fly away if touched during the day.


Gardeners also can turn to pesticides to defeat Japanese beetles, but Maddox warned that the compounds can injure bees and other pollinators. He reminded vegetable gardeners to check that pesticides would not render their harvest inedible.



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