重大植物病害之認定及其因應措施

Abstract

植物病害種類可以分成生物性(傳染性)與非生物性(非傳染性)兩大類。引起生物性病害的病原有真菌、細菌、菌質、線蟲、濾過性病毒及寄生性高等植物等等；而造成非生物性的因子則有凍傷、日燒、乾旱、藥害、肥傷、風害、冰雹、雷電、機械傷害及環境污染等。很多生物性引起的病原具高度傳染性，一旦流行傳播，往往造成作物減產和重大經濟損失。本文僅以1970 年代末期在美國、加拿大及1980 年代初期在日本首次發現的病害苜蓿黃萎病(Verticillium wilt of alfalfa 由真菌Verticillium albo-atrum 引起)為例，來討論有關重大植物病害之認定及其因應措施等問題。本病自1976年在美國西北部苜蓿田首次發現後，迅速蔓延到美國和加拿大很多地區，而成為眾所關注的重要病害。它之所以能受到有效控制是歸功於積極進行病害調查和研發有效病害防治策略如加強防、檢疫工作和開發新抗病品種等。 Plant diseases may be due to biotic factors such as fungi, bacteria, mycoplasma, viruses, nematodes and parasitic plants or abiotic factors such as freezing injury, sun scorch, drought injury, injury of agrochemicals (pesticides and fertilizers) or environmental pollutants, wind damage, hail injury and mechanical injury. Most of the biological agents are contagious and capable of spreading via infected plants. A crop disease is considered high risks if it spreads rapidly and causes severe economic loss. The outbreak of a new crop disease will likely draw attention but its potential impacts depend upon mode of infection and means of spreads of the pathogen as well as economic impacts of the disease. Verticillium wilt of alfalfa, an important disease in Europe since 1918, was first found in some commercial fields of alfalfa in North America in 1976. The disease spread rapidly to all major alfalfa production areas in the USA and Canada in 1980s and 1990s because of numerous methods for dispersal of the pathogen and lack of resistance in commercial alfalfa cultivars. The outbreak of this disease in North America is used as an example to discuss strategies for assessment and management of new and high impact diseases in crops.