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Episode 02

Why Did a Japanese Town Pay ¥100 for Each Beetle?

Kawajima paid ¥100 per dead beetle and ran out of money in 45 days. The invasive beetle kills cherry trees from inside, and summer is the only time to catch it.

26 October 20266 min readVideo 8:20

A Japanese town paid ¥100 a beetle because an invasive beetle kills cherry, plum and peach trees from the inside, where spray struggles to reach and felling is the surest cure. Its adults are only outside from late May to August and can mate at once, so a beetle caught in summer lays no more eggs. And the people who walk past the trees every day are the ones who can spot it.

Watch the episode: Why a Japanese Town Paid ¥100 a Beetle 8:20

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The town that ran out of beetle money

From 1 June 2026, Kawajima, a town in Saitama Prefecture, paid ¥100 in cash for each adult beetle brought to the town office. Kawajima had first found the beetle in 2024, and damage to its cherry trees began to be reported soon after.

The first budget, about ¥150,000, covered 1,500 beetles. It was gone by mid-June. After an emergency top-up, the ¥7 million cap was reached on 16 July and payments ended, in a scheme planned to run to the end of September. That's 70,000 beetles in 45 days, more than 1,500 a day. A town official said no single municipality had ever killed so many.

The rules were strict. Carrying the beetle alive is illegal, so it had to be killed where it was found. It only counted if its red chest could be seen. Larvae earned nothing.

So I wanted to know why a town would pay cash for dead insects, and why the national government would set up a task force for one beetle.

What is this beetle?

It's a shiny black beetle, 2.5 to 4 cm long, with a red chest that looks like a neck. The male's antennae are longer than its body. It has its own smell, which Wakayama Prefecture's control manual suggests may be musk or lychee.

It's native to places like China and Vietnam, and probably reached Japan with the movement of goods. In Europe, its main pathway is probably wood packaging: it was reported in Bavaria, Germany, in 2011 and 2016, and in Italy first in 2012, in Campania, the region around Naples.

In Japan, the first adult was found in Saitama in 2011, a year before the first damage was confirmed in Aichi Prefecture in 2012. It attacks cherry, plum, peach and other Prunus trees, and its larvae eat them from the inside. A badly damaged tree dies. In 2018 Japan designated it an invasive alien species, so keeping, importing or releasing one is banned. That's why Kawajima wanted them dead.

Why doesn't spraying stop it?

A female lays her eggs in cracks in the bark, about 300 to 1,000 of them. Here is what happens next, according to Wakayama's manual:

After about 10 days, the eggs hatch and the larvae bore into the tree.
They grow inside it for 1 to 3 years. More than 200 have been found in a single tree.
They push out frass, a mix of wood shavings and droppings, in large amounts.
Before becoming an adult, each larva seals itself into a chamber with a tough, cork-like lid and stays shut in for more than half a year.
Adults come out from late May to about August, leaving the tree through an exit hole.

The frass is the main clue from outside. Gunma Prefecture says it's often shaped like karintō, a fried snack. I may never look at karintō the same way.

The trouble is reaching the larvae. Once damage advances, pesticides work less well and complete removal is hard. The larva gets under the bark fast, insecticides are generally ineffective against larvae, and control relies mainly on removing infested trees. In Osaka Prefecture, more than 14,000 cherry trees were damaged and more than 1,500 cut down, as of February 2026.

A damaged tree left standing can be wrapped in netting with a mesh of 4 mm or less, which stops the adults spreading. No single method works on its own, so several are combined.

That leaves one weak moment. Adults are active by day, moving about the trees in the heat, and they can mate right after emerging, so they must be killed on the spot. Osaka's advice is direct: step on it, or spray it.

How fast is it spreading?

On its own wings, an adult travels about 2 to 3 km a year, and most new outbreaks are within 3 km of a known one. But some appear about 40 km away, more than 13 years of flying. Wakayama's first find, a male in July 2017, was sitting on a small kei truck.

In 2024, damage had been confirmed in 14 prefectures. By September 2026 it had reached 22 prefectures and more than 300 municipalities, and six found it for the first time in 2026. In Saitama, damage sites rose from 931 to 1,391 in a year, in 56 of the prefecture's 63 municipalities.

A forecast by the National Institute for Environmental Studies and Nippon Institute of Technology says that, without control, it spreads over almost all of Honshu and Shikoku by 2050 and into Kyushu. It has the beetle in Kanto and part of Kansai by 2030, then reaching Hokkaido, and assumes beetles also ride tens of kilometres hidden in cars.

Why pay people to catch it?

Famous cherry spots and landmark trees are being lost, and the government fears for tourism. Damage to plum, peach and Japanese plum crops is growing fast. In Wakayama it first damaged a peach orchard in Katsuragi in November 2019, and by May 2023 it had reached the centre of the prefecture. Since fiscal 2022 the agriculture ministry has paid to replant damaged fruit trees, one tree at a time.

On 31 July 2026 the government set up a task force headed by the agriculture and environment ministers. Its strategy aims to stop the spread now and set a path to shrinking the damaged area by fiscal 2030, with nationwide eradication as the long-term goal. So 2030 is the deadline for a path.

Then came money. On 6 October 2026 the environment ministry released ¥2,704 million from reserve funds for local governments, and the agriculture ministry got ¥528 million for orchard surveys and control. Together that's about ¥3.2 billion: at ¥100 a beetle, 32 million beetles. For fiscal 2027 the environment ministry asked for ¥6.7 billion to fight invasive species, led by this beetle.

The environment ministry also spends money from the International Tourist Tax, charged on each departure from Japan, which rose to ¥3,000 on 1 July 2026. Every visitor who leaves helps pay to save the trees they came to see.

Kawajima wasn't alone. In 2025, Fussa, in Tokyo, gave ¥500 in shop vouchers for every 10 beetles, up to 100 per person. Osaka gave prizes, such as Tennoji Zoo guided tours and Cerezo Osaka football goods, to the 20 people who brought in the most beetles between 1 June and 28 August.

The national strategy asks landowners, farmers and residents to watch Prunus trees and report adults or frass quickly.

Look at the ground by the trunk

Once the larvae are inside, a tree is hard to save, and a beetle caught in summer can't lay more eggs. ¥100 a beetle got about 70,000 caught in the weeks they were out, by the people who pass those trees every day.

Next time you're under a cherry tree, look at the ground by the trunk. Saitama asks residents to check trees in parks, on riverbanks and at schools, because frass piles up at the base. A small pile shaped like a snack may mean the beetle is there.

Would you spend a summer catching beetles for ¥100 each?

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