Japanese Beetles Ransack Rose Garden—And Yours

They seemed to come from nowhere, suddenly appearing on what felt like every branch, petal and leaf in Southwest. Crawling. Flying. Climbing. Gnawing.

After a week or so in the grasp of thousands of tiny mandibles from a species of scarab beetle called popillia japonica—or Japanese Beetles—many area plants have been left looking like swiss cheese, or worse.

As if Southwest's gardeners needed more to contend with after a summer of wild swings in temperature and sudden, ferocious downpours.

The most public devastation is happening at Lake Harriet's Rose Gardens, where many of the leaves and flowers have been reduced to skeletons. And gardeners all over Southwest Minneapolis are watching months of personal care nibbled away in a matter of weeks.    

The beetles "have taken large chunks out of a variety of foliage all over my neighborhood," Sharon Hedrick wrote on the Facebook page of Southwest Minneapolis Patch.

"My roses are being destroyed by Japanese beetles," said Erin Hooper. "I'm trying to spray them away with pesticide, but they aren't leaving!"

Peggy Poore of Southwest Minneapolis's Uncommon Gardens, said the local Japanese Beetle population has exploded this year. One visit to the Lyndale Park Rose Garden is enough to see the creatures' depredations. Typically in bloom this time of year, the garden is riddled with whithered, rotting blossoms and yellowed leaves. Many of these wounded plants are covered with masses of the shiny blue-black creatures.

No surprise—roses are one of the beetles' favorite foods, according to the University of Minnesota's Extension school. The beetles also target trees, including some American Elms that line Minneapolis' streets. So far, said city Park Board officials, they haven't noticed extensive damage to the trees.

"Oh, that's just like with our basil back home," said Marlene Jue, an Ohio native in town visiting her daughter, as she bent over some of the Lyndale Rose Garden's damaged plants.

The little invaders first appeared in North America in 1916, according to the University, when they were accidentally introduced to New Jersey from Japan. Since then, the beetles have spread steadily westward, arriving in Minnesota in 1972. Japonica numbers are kept in check on the East Coast by two kinds of soil-dwelling, single-celled organisms that reduce numbers of beetle grubs, but no such biological countermeasures exist in Minnesota, according to a fact sheet from the school.

"Our pest company sprayed a combination of products on the beetles, which seems to have scared them away," Hedrick wrote. "My understanding is that the Japanese Beetle has a grub cycle, so it is also necessary to treat the ground where they lay their eggs. I am still working on that part.

Some Minneapolis gardeners have spent time scraping beetles off their leaves into cups or buckets of soapy water—a beetle dunked into this mixture dies within seconds. But for the dozens of beetles that even the most patient and obsessive gardener can deal with manually, scores more await.   

Jue said she and her son Alexander tried a number of different remedies to get rid of the beetles, including spraying soapy water on the basil.

"We couldn't get rid of them!" she said.

The United State Department of Agriculture has produced the comprehensive "Managing the Japanese Beetle: A Homeowner's Handbook." The USDA has compiled other resources here.

Uncommon Gardens' Poore said her business has so far not been hit badly, but only out of luck. 

The University's extension school recommends going after the beetles's larvae with pesticides. But with the beetles currently in the middle of their adult mating period, according to Poore, the best remedy is picking the beetles off plants as you see them, before they eat your plants to pieces.

However dire the floral situation may seem right now, said Poore, the end is in sight.

"The cycle is almost over," she said. "They won’t be around much longer. A lot of plants will survive—they'll just look bad."