The red-necked longhorned beetle, an insect designated as a specified invasive alien species in 2018, has now spread to 13 prefectures around the nation and destroyed many of Japan’s beloved cherry trees.

Vigilance and countermeasures have been taken at various popular cherry blossom viewing spots. But in some areas, rows of cherry trees have been felled because of the beetles.

A research facility for agriculture, forestry and fisheries located in Habikino, Osaka Prefecture, had been open on weekends in spring to let residents enjoy the sakura.

But three years ago, more than a dozen cherry trees there were cut down because of the beetle infestation, leaving only a few trees standing.

“I thought these trees would be there forever,” said a 21-year-old university student who lives nearby. He still has a picture of his family under the blossoms at the facility when he was a child.

According to the environment ministry, the beetle species, called “kubi-aka-tsuya-kamikiri” in Japanese, originally inhabited China and the Korean Peninsula.

Its body length is 2.5 to 4 centimeters. And as its name suggests, the bug has a red neck and a glossy black body.

Experts believe the species’ eggs and larvae likely entered Japan in imported lumber.

The red-necked longhorned beetle has a habit of laying eggs--300 to 1,000--on cherry, plum, peach and persimmon trees. The larvae spend one to two years devouring the inside of the trunk, which weakens and eventually kills the trees.

The first damage from the beetle in Japan was reported in 2012 at Nagoya Port in Aichi Prefecture.

The beetles then spread, leading to the government’s invasive species designation because of the insect’s impact on ecosystems and the agriculture, forestry, and fisheries industries.

The first damage from the beetles around Mount Yoshinoyama in Yoshino, Nara Prefecture, was confirmed in 2023, on peaches in a vegetable garden about 7 km from the mountain.

The area is renowned for its thousands of cherry trees blooming in spring.

Last year, three workers of a local group that works to protect and preserve cherry trees spent several hours a month from April to October checking for beetles and eggs on about 200 cherry trees near the entrance to the mountain.

“If the (beetles) get into the area, it will be a big problem,” a group representative said. “We will continue to be vigilant.”

The Takada-senbonzakura area in Yamatotakada, Nara Prefecture, is a 2.5-kilometer stretch of cherry trees that are over 70 years old. The city government has carefully managed about 450 trees in the area.

In 2023, officials found beetle damage in about 150 of the trees.

The trees were not near death, but the city allocated 5.7 million yen ($37,500) in the fiscal 2024 budget to inject chemicals into the trunks to exterminate the larvae.

In Tokyo, damage from red-necked longhorned beetles was first confirmed in 2015 in Akiruno and Fussa cities, both western suburbs of the capital.

By 2022, the number of affected trees had increased to nearly 500 in the metropolitan area, and the damage to cherry trees was particularly noticeable.

In June 2023, larval parasites were found on “someiyoshino” cherry trees in Sumida Park in Tokyo’s Sumida Ward, a popular cherry blossom viewing spot since the Edo Period (1603-1867).

According to ward officials, volunteers who were trying to preserve cherry trees found the infestation.

Seven of the 125 cherry trees, known as “bokutei-no-sakura,” along the Sumidagawa river in the ward were also damaged.

Workers look for “frass,” a mixture of larval feces and wood debris, to determine if the larvae are in the trunk.

The Akiruno city government has started a system that lets citizens who find frass or adult larvae to scan a QR code on their smartphones and send in the location and a photo.

The city said 144 cases had been reported through the system in fiscal 2023, of which 126 were confirmed as red-necked longhorned beetles.

In Aichi Prefecture, officials were temporarily able to control the situation after the first damage was reported in 2012 by cutting down trees and injecting chemicals.

However, in 2019, the beetles were confirmed in its capital city of Nagoya and have now spread to eight municipalities in the prefecture in central Japan.

On the main southern island of Kyushu, no beetle damage has been confirmed. However, the city government of Aso in Kumamoto Prefecture has posted characteristics and ecology of the invasive species on its website to bring the problem to the attention of residents.

In Oyama, Tochigi Prefecture, the city government has offered 500 yen for every 10 dead adult beetles since fiscal 2019.

By fiscal 2022, the number brought in was zero. But in fiscal 2023, when the damage to trees was more extensive, the city received 33 specimens.

Other municipalities have adopted similar incentive programs.

“Japan is a paradise for the red-necked longhorn beetle,” said Takuto Hirooka, 37, a researcher at a Wakayama prefectural government’s research facility that studies fruits, such as persimmons.

The facility has been at the forefront of prevention and extermination efforts against the invasive species.

There are no bees that can serve as natural enemies to the beetles in Japan, and the countries has many trees that the insects prefer, including cherry varieties.

Although adult beetles can travel only 2 to 3 km, they can move long distances on cars and other vehicles, Hirooka said.

“Cherry trees are also planted in parks and riverbeds, so it is not surprising that the damage could spread anywhere,” he said.

To battle the insects, it is important to “quickly find the damage and take countermeasures,” Hirooka said.

Damaged trees show large numbers of frass from around May.

Hirooka urges people to report such sightings to the environment ministry and local governments as soon as possible.

(This article was written by Junichi Takitsubo and Mami Okada.)