Pine wilt disease plagues South Chungcheong forests with 28-fold increase in a year

Pine wilt disease, a parasitic infection that rapidly kills pine trees, surged 28-fold along South Chungcheong's west coast in a single year, triggering an emergency response from forestry authorities who have poured 185.8 billion won ($133 million) into nationwide efforts to limit the damage.

The number of trees affected by pine wilt disease in the province rose from roughly 5,000 between May 2024 and May 2025 to 139,922 this year, according to the Korea Forest Service (KFS) and South Chungcheong provincial office on Wednesday.

By region, Taean County recorded 34,783 infected trees, Boryeong 31,751, Cheongyang County 31,717 and Seocheon County 31,427. These four cities and counties account for 92 percent of all infected trees in South Chungcheong.

Pine wilt disease is a lethal pine tree disease caused by a microscopic worm called the pine wood nematode, which is spread by the pine sawyer beetle when it feeds on healthy trees. Once inside a tree, the nematode blocks its water-conducting tissue, causing it to wilt and die within weeks to months. There is no cure once a tree is infected, so control efforts focus on removing the infected trees and killing the beetle vector before it can spread further. The disease is native to North America but has proven especially destructive in Asia, where pine species lack natural resistance to it.

The province and local governments are removing infected and damaged trees, administering preventive injections, planting different tree species and using drones to control pine sawyer beetles. Trees with conservational value, such as the Anmyeon pine trees on Anmyeon Island in Taean, are being protected through injections.

To fund these efforts, South Chungcheong and Taean County recently requested budget support from the KFS, with South Chungcheong Vice Gov. Hong Jong-wan meeting KFS Commissioner Park Eun-sik at the Government Complex Daejeon on Aug. 12 to request 20 billion won in funding for next year's pine wilt disease control program.

The central government's budget devoted to pine wilt disease control this year alone reaches 185.8 billion won, comprising a base budget of 100 billion won plus an additional 85 billion won in disaster relief funding.

The South Chungcheong government also requested that Boryeong, Seocheon and Cheongyang also be designated special quarantine zones, following Taean's designation last Friday. A special quarantine zone is a classification for an area where damage has reached the "severe" level or above — defined as a city, county or district with 30,000 or more damaged trees — that a local government applies for, subject to review and official designation by the KFS. Once granted, year-round pest control is permitted.

The KFS is also moving to establish a "national control belt" which designates a "response zone" within 2 kilometers (1.25 miles) of the outer edge of severely affected areas — where the disease is most likely to spread to surrounding forests — for intensive control efforts, along with a buffer zone determined based on the pace of spread.

“If the government budget [of 15 billion won annually] is finalized, we will be able to establish a national disease-control belt next year,” an official from the KFS' pest control division said.

The agency said this year's pine wilt disease infections are a "third major outbreak" following major outbreaks in 2007 and 2014. A total of 1.77 million pine trees died from the disease nationwide across 166 cities, counties and districts in 16 provinces and metropolitan cities between June 1 last year and May 31 this year, it said.

The disease was first detected in Korea in 1988, with the first major outbreak in 2007 killing 1.37 million trees, followed by a second in 2014 that destroyed 2.18 million trees. Infections then began to decline until 2022, when 380,000 trees were recorded dead. 

Experts argue that aerial pesticide spraying, suspended in 2023, should be resumed for effective control. The KFS had conducted aerial spraying over large areas of pine forest each year, covering 8,600 acres in 2020. But it halted the practice in February 2023 amid strong opposition from environmental groups and some political circles citing environmental pollution concerns.

Pine wilt disease spread rapidly after the suspension.

"Success in controlling pine wilt disease depends on how effectively the vector insect — the pine sawyer beetle — is controlled during its emergence period, from May to July, peaking in mid-June, when it transforms from pupa to adult and emerges from trees," Nam Sung-hyun, former commissioner of the KFS, said. 

"If adult beetles are not controlled during the emergence period, an explosive spread of infection across entire forests is only a matter of time. The suspension of aerial spraying has had an impact on the spread of the disease, and aerial spraying is an effective control method for large areas."

A KFS official said the commission is weighing whether to expand aerial spraying. "This year, we conducted a pilot aerial spraying operation using environmentally friendly pesticides in Pohang, North Gyeongsang, and we will decide next year whether to expand it," he said. 

BY KIM BANG-HYUN [[email protected]]