有機農法的作物病害管理技術

Abstract

推動有機栽培農法不但可以維護環境生態的穩定與和諧外，尚可確保糧食生產安全。由於栽培制度的改變，近年來有機栽培田常出現的作物病害有：白菜炭疽病（Cruciferous vegetable anthracnose）、萵苣褐斑病（Acremoniumbrown spot of lettuce）、萵苣萎凋病（Fusarium wilt of lettuce）、莧菜葉斑病(Rhizoctonia leaf spot of amaranth)、蔬菜幼苗立枯病（Rhizoctonia blight ofvegetable）及白絹病（Southern blight）等等。有機農作物的病害管理觀念，是以「共存」作為防治策略的執行準則，因此在整個有機農業生態體系中，均應確認農作物、植物病原、媒介者、拮抗微生物、天敵及環境等因子是它固有的基本成員，是故作物病害的管理系統須先釐定作物經濟損失門檻（Economic loss threshold），進而以病原的生態特性及傳染病學作為研提防治策略的基礎，設計病害預測模式外，並且執行合理化、多元化的病害防治技術，才能有效達成管理作物病害的目標。管理有機農作物病害的主要手段，即是1.降低病原的最初接種源（initial inoculum）與2.降低病原的傳播與感染速率。歸言之，有機作物病害的管理技術須優先嚴格執行法規防治（拒病）外，尚須全盤掌握整個農業環境與明瞭農作物與病原的各種生態特性，有效融入各種病害防治法，才可達到防治作物病害的效益。執行病害管理的過程尤應適時、適地，且合乎經濟與生態法則的採納作物輪栽制、選擇適當的種植時間與地點、注重田間衛生管理、加強種子處理、培育健康種苗、採用抗病根砧及施用生物製劑與有機添加物等技術。 Organic farming practices should be considered not only to preserve stabilization of agroecosystem, but also to ensure production of food safety. However, due to change of cultural practice, several crop diseases such as cruciferous vegetable anthracnose, Acremonium brown spot of lettuce, Fusarium wilt of lettuce, Rhizoctonia leaf spot of amaranth, Rhizoctonia blight and southern blight of vegetable have become more severe in Taiwanese organic fields. In organic farming system, the integrated disease management strategy (IDMS) is devised to counteract plant diseases with respect to ecological and environmental niche. This process of consolidation has focused attention on more practical needs of moving the ideas and the techniques to conduct IDMS in the organic fields and maintaining the pest population density below economic injury level. There are essentially some principles basis for the IDMS involved: first, understanding detailed information including pathogen life cycles and crop physiological requirement; second, developing diversified controls coordinated to achieve an additive or synergistic effect; third, considering yield losses and developing economic thresholds; and four, qualifying ecological and environmental assessment to minimize a detrimental effect on non-target organisms. Accordingly, the IDMS must aim at reducing the initial inoculum and the rate of infection and spread of the pathogen. However, apart from the prosecution of exclusion, the optional techniques available for IDMS of organic farming include crop rotations, adjustment of planting dates and places, tillage systems, the use of pathogen-free seeds or seedlings, disease resistant root stock, microbial agent and organic soil amendments.