A tree disease is causing leaves to turn red and wither at the foot of the Shirakami mountains. (Video by Kazuhiro Nagashima and Shigetaka Kodama)

A seemingly unstoppable disease is causing trees to wilt near a UNESCO World Heritage site, threatening the local ecosystem and ruining the famed blazing autumn foliage at the border of Aomori and Akita prefectures.

Aerial images show leaves in forests at the foot of the Shirakami mountains have turned red and are withering, a tell-tale sign of the disease.

The condition is caused by ambrosia beetles, which carry a type of mold known as Raffaelea quercivora in the several-millimeter-long bodies.

The mold invades the trunks of broad-leaved trees, such as Japanese oak, chinquapin, evergreen oak and other types of oak, and blocks the water flow inside. This causes the trees to wilt.

According to the Aomori prefectural government, only 85 trees were confirmed affected by the disease in the town of Fukaura in the prefecture between July 2016 and June 2017. But the number suddenly rose to 2,409 for the period from July 2018 through June 2019.

There are no effective preventive measures against the disease, so infected trees must be cut down or fumigated.

But the trees need to be treated one by one. And it is extremely difficult to deal with infected trees that are on steep slopes or deep in the mountains, making it nearly impossible to completely prevent the disease from spreading.

Officials are worried that the wilt condition could reach the core of the Shirakami mountain range, which in 1993 was named a UNESCO natural World Heritage site, and damage the local ecosystem.

Ritsuko Hamada, 55, a member of a nonprofit organization that has surveyed animals and plants in Shirakami for more than 10 years, said nuts from Japanese oaks are an important food source for bears and mice.

“If trees continue to wither, the balance of the whole ecosystem in the Shirakami mountains could be spoiled,” Hamada said.

Masa Abo, 92, who lives in Fukaura’s Omagoshi district and grows white and sweet potatoes, said hordes of mice that have been driven out of forests by the tree disease are invading nearby human settlements.

“The crops I carefully grew were bitten by mice,” said Abo, referring to the unprecedented damage to her potatoes in an agricultural field. “There may be nothing to eat in the mountains.”