DONNAS, Italy (AP) — The iridescent green beetles native to Japan have become a growing menace in Italy, swarming through orchards and vineyards and leaving behind devastating lattice patterns in leaves that weaken the plants and reduce production.
The Popillia japonica, or Japanese beetle, is a familiar pest in the United States, where it arrived more than a century ago.
But it is a relative newcomer to the European continent, first detected near Milan’s
Malpensa airport in 2014. In Italy, it has already swarmed through the northeastern regions of Lombardy, Piedmont and Valle d’Aosta, where it appeared last year in terraced vineyards above the town of Donnas.
“We’re seeing the popillia steadily advance from terrace to terrace across our historic vineyards," said Luciano Zoppo Ronzero, a winemaker who produces Nebbiolo from the terraced vines. “We’re now about the 10th terrace and can already see the popillia attacks. This means they’re consuming and gradually moving up the mountain.”
With no natural predators and an appetite covering over 300 plants and trees, the Japanese beetle has made the European Union's list of priority pests, meaning that efforts must be made to contain and eradicate outbreaks.
The beetle is already entrenched in Italy, Switzerland and Germany, where the focus is on managing and containing expansion, while the population levels in France and Spain still allow hopes of eradication, said Daniela Lupi, an entomologist at the University of Milan.
The Japanese beetle is voracious and travels en masse as it feeds. Adult beetles also hitch a ride on trains, cars and airplanes. After spending summer months feasting, the beetles mate and their larvae feed on grasses until reaching maturity, and launch the cycle anew.
The Coldiretti agricultural lobby says the pest poses a major threat to agriculture as it makes its way through the Po River Valley, Italy’s breadbasket. But damage so far has been hard to quantify because often the beetle’s pattern of eating away the pulp of leaves weakens the plant, lowering production, without necessarily killing healthy plants.
“In some areas, the beetle has destroyed the harvest,’’ said Lorenzo Bazzana, the head of economic affairs at Coldiretti. The larvae, known as grubs, also feed on grass roots, damaging lawns, golf courses and playing fields.
Zoppo Ronzero is concerned for both his historic terraced vineyards, carved into the mountainside and stabilized by centuries-old drystone walls, and for his production. By defoliating the vines, the beetles expose grape clusters to the sun while severely reducing the plants’ ability to photosynthesize.
“What scares me is the fact that in the end the grapes don’t ripen. If the grapes don’t ripen, it means we’re not bringing home a splendid harvest, as we had hoped, but something unusable,” Ronzero said.
The best hope for eradicating the pests is attacking the larvae, according to Bazzana. The beetles were recently detected near Verona’s Valerio Catullo airport, and experts are experimenting by introducing a microscopic parasite in the surrounding area to attack the grubs.
Pheromone traps are also widely used, while the wine producers in Donnas are relying on pesticide treatments, even though the effectiveness is short-lived and labor-intensive on the steep terrain.
“If we don’t counter it, the population will continue to rise and so there will be strong damage to the fruits plants, to the grasses, to the ornamental plants,” Lupi, the entomologist, said. “There are no problems for the human population, because they are not so dangerous, but the production is really, really lowered.”
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Associated Press writer Colleen Barry in Milan contributed to this report.
