But the sudden death of large patches of pine forest and the explosion of nematode populations in Asian countries leads researchers to conclude that the worms must have arrived from abroad. With an increasing flow of goods and people around the world in the 20th century, the pine wood nematode must have come from North America to Japan and from there to Taiwan.
亞洲國家卻出現線蟲族群爆炸、大片松林致死，研究人員遂斷定它是放洋而來，尤其在交通日益頻繁，貨物暢流的二十世紀，松材線蟲應是由北美被帶至日本，再轉道台灣。