Come June, the dreaded Japanese beetle season will be upon us and rose-lovers like Amelita Cresswell will shift into search-and-destroy mode.

She'll either spray with a powerful insecticide or knock the iridescent green-and-bronze bugs off her bushes, one by one, into a quart jar containing bleach and water. "Sounds crude and rude, but you're essentially drowning them," says the unrepentant Cresswell, who cultivates about 350 roses on her 14-acre farm in Dresher.

Soon there may be a new weapon available in the war against Popillia japonica, which feeds on 300 species of garden plants, fruits, vegetables, and turf, and is considered a major scourge in the eastern United States.

It's pretty simple: Scientists at the U.S. Department of Agriculture have determined that the flower petals of the common geranium can be deadly to the Japanese beetle.

In experiments at the USDA's Agricultural Research Service in Wooster, Ohio, within 30 minutes of consuming red, white, or salmon geranium petals, the beetles rolled over on their backs, legs and antennae slowly twitching, and became paralyzed.

They recovered within 24 hours, but here's the beautiful part:

Were this to happen outside the lab - say, on a golf course, in fields of corn, soybeans, or grapes, or in backyard gardens - the immobilized beetles likely would dry up, rendering them easy prey to ants, birds, toads, and moles.

"Oh, my goodness, that's amazing," says Cresswell, who wondered whether she should plant a boatload of geraniums in her rose garden once the danger of frost is past, usually right about now.

In a word: No.

"At this point, I wouldn't run out and buy geraniums and expect there to be no more Japanese beetles," says entomologist Christopher M. Ranger, a native of Gillette, N.J., and lead scientist on the beetle project.

"But it does look promising," he says. "Ultimately, we can develop pest-control strategies for homeowners to use, based on this whole phenomenon."

Those strategies, which the USDA hopes to patent, likely involve isolating the paralyzing geranium compounds and using them to create a natural botanical spray to control beetles. It's a huge issue.

More than $450 million is spent each year to control them and to replace damaged plants, the USDA estimates.

And it all started in New Jersey.

Kept in check by predators at home, this destructive pest was first discovered in North America in 1916, during an inspection at a plant nursery in Riverton. It has since spread as far west as Sacramento and San Diego, where Ranger says outbreaks have been eradicated with insecticides.

"California remains extremely paranoid about it," he says.

The beetle's dangerous affinity for geraniums was initially suggested in a research paper in 1920, confirmed in 1929, then dropped until the late 1990s, when a doctoral candidate at the University of Kentucky replicated the successful experiments.

Ranger, who has graduate degrees from both Pennsylvania State and Rutgers Universities, picked up the trail in 2006, when he joined the USDA. Though he acknowledges the "ick factor" of Japanese beetles, Ranger finds them fascinating.

He's been enamored of insects since seventh grade, when he overheard his fly-fishing instructor and another fisherman trying to identify the may fly they'd just seen. Now, as an entomologist, he specializes in the interaction between insects and plants, especially the chemicals that affect those interactions.

Before the Japanese-beetle project, Ranger worked on improving the aphid resistance of blueberries at the Philip E. Marucci Center for Blueberry and Cranberry Research, a Rutgers facility in Chatsworth, Burlington County.

At the USDA lab in Ohio, Ranger focuses not just on adult beetles, but also on the grubs, or larvae, which are very damaging, too.

Grubs hibernate underground in winter. As the soil warms up in spring, they gorge on grass roots, eventually causing brown patches and lawn death.

In late June they morph into the familiar iridescent green and bronze beetles that binge-eat their way through the garden till mid-August, by which time they've produced a new generation of grubs underground.

And so it goes.

"Japanese beetles are a big problem. They eat everything in sight," says Bruce Monroe, who babies about 100 roses in New Castle County, Del., and belongs to rose societies in Philadelphia, New Jersey, and Delaware-Chester Counties.

But, he says, keep in mind that beetle infestations go in cycles. Last year wasn't too bad in the Philadelphia area. 2008, on the other hand . . .

"I've been growing roses for 30 years and there's no such thing as a normal year," says Monroe, who sprays with insecticides when it's bad. Others use biological controls, such as horticultural oils, on the leaves or milky spore bacteria on the lawn, which kills the grubs.

Gardeners also try to plant more things beetles don't like, such as hollies, hydrangeas, rhododendrons, and lilacs.

But for getting rid of beetles on roses, Judith C. McKeon of Andorra is of the old school. "The most low-tech and best method is picking them off and dropping them into soapy water, especially the first to arrive in the garden, as these attract others to fly in from miles around," she says.

If you can kill off that first beetle wave, "that's the most important thing," says McKeon, author of Gardening With Roses and The Encyclopedia of Roses. From 1984 to 1999, she also was chief rosarian, as ardent rose-growers are known, at Morris Arboretum in Chestnut Hill.

Monroe outsmarts the beetles by planting older rose varieties that bloom in early June and again, meekly, in September, a cycle that misses peak beetle season. (Those with more modern, ever-blooming roses, such as the Knockout series, get zapped all summer.)

"I really don't worry too much about beetles," Monroe says.

He also doesn't bother with beetle traps that attract with sex hormones and floral scent. Studies show they draw more beetles than they kill.

Cresswell, for one, is looking forward to trying the USDA's geranium strategy on her Japanese beetles, when it finally comes to market. Meanwhile, she asks, can someone help with rose midge, an even bigger problem?

This tiny pest - first reported in the United States in 1886, in New Jersey, once again - looks like a fruit fly, reproduces like crazy, and lays its eggs right in the rosebuds. When the eggs hatch, your buds are history.

"They eat all the blossoms. Terrible," Cresswell says.

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