It's not been a good year for the roses.

Frustrated home gardeners probably are intimately familiar with Japanese beetles, which belie their iridescent purple good looks by wreaking havoc on roses, raspberries, beans, cannas, linden trees and Virginia creepers, among others.

The Lake Harriet Rose Garden in Minneapolis has become a large-scale beetle buffet, and the insects also are dining at the Minnesota Landscape Arboretum in Chanhassen, too.

Japanese beetles were first documented on the East Coast in 1968. Over the decades, they've eaten their way westward. The state experienced a few bad years early in the last decade, but then the beetles' numbers dropped way off, said Jeff Hahn, an entomologist with the University of Minnesota Extension Service. By 2005, though, he started getting more and more phone calls and complaints. Judging from the calls and e-mails from gardeners and the comments he's heard from colleagues, Hahn said, this could be one of the worst years yet.

The beetles spend much of the year underground, emerging from July to September to mate and eat. They are susceptible to drought and a few fungal conditions, but they have few natural enemies in the United States. Pesticides have limited effectiveness, and even if gardeners manage to kill the ones in their garden beds, a new batch could fly in at any time.

On the East Coast, the scourge fluctuates. That's likely what will happen here, after another bad year or two, said Jeff Gillman, an associate professor of horticulture at the University of Minnesota, who also has lived in beetle-worn Georgia and Philadelphia.

"It's going to get worse before it gets better," he said. "The Japanese beetle is going to increase another year, then we could see them on a year or two then off a year or two."

Damage not permanent

After a beetle invasion, valued plants and trees are unsightly, but they rarely will have permanent damage. They will leaf out again this year, and may produce more blooms.

"They don't really kill the plants," Miller said. "They put holes in them and cause trouble, but that's not something that's going to completely wipe out a plant unless the plant is stressed out to start with."

On a recent morning, the garden at Lake Harriet was not the usual late-July riot of color, but an expanse of green and brown, with a few lonely spots of yellow and pink. A closer look found a few of the blooms crawling with munching beetles. At least nine crawled over a partially open bloom of an apricot-colored Abraham Darby rose.

That's an improvement, said gardener Jeremy Mickelson, noting that during the third week of July, it looked like a plague had hit the gardens.

Behind the work shed at the park, Mickelson showed a trio of potted shrub roses, their blooms stripped, their leaves denuded to the brown ribs.

Taking aim

Because of the garden's proximity to Lake Harriet, and to minimize harm to beneficial insects like honeybees, workers at the Rose Garden use an over-the-counter pesticide. This week, a few hours after Mickelson and other workers applied a second Orthene pesticide treatment in two weeks, a few of the beetles moved sluggishly across the leaves, or lay on their backs, legs splayed.

During the worst of the scourge, volunteers were dispatched to pluck the beetles off the rosebushes, cannas and crab apple trees and drown them in soapy water, the treatment most recommended to homeowners. But with more than 1,500 rosebushes alone at the garden, that's a never-ending job.

At the Minnesota Landscape Arboretum, dealing with the beetles is an exercise in tolerance, said Dan Miller, an integrated pest management specialist. In the Wilson Rose Garden, there's little tolerance for stripped leaves and chewed-up blooms. People who visit the garden -- and plan summer weddings there -- expect a high standard for its appearance. Gardeners have been treating the fussy hybrid roses with a commercial product called Tempo, a permethrin, one of the treatments deemed to be least harmful to bees.

That's not the case with the Nelson shrub rose garden, elsewhere on the grounds. Those old roses are a little more resilient. A wait-and-see approach is also being taken with other areas.

"We have to learn to live with them, like people on the East Coast have been living with them for a long time," Miller said. "We have to learn to pick our battles."

Maria Elena Baca • 612-673-4409