氣象因子對台灣晚疫病發生率之影響

Abstract

晚疫病(late blight, LB)由Phytophthora infestans (Mont.) de Bary 所引起，主要危害茄科作物，包括番茄、馬鈴薯等，是世界上重大作物病害之一。台灣平均溫度偏高，並不適合病原晚疫病菌生長，但由於致病力強的新菌系出現，使得1998年後晚疫病成為台灣番茄及馬鈴薯最主要的病害之一。 晚疫病的發生受到氣象因素的影響甚深，台灣與世界主要疫區相比，氣溫要高出許多，並不利晚疫病的發展，但新菌系的入侵造成台灣大規模的疫情產生，推測台灣氣象因子對新菌系誘發病害的影響，與往昔對舊菌系影響有相當差異。因此本研究即針對新菌系在副熱帶季風氣候的台灣地區，進行氣象因子對晚疫病影響之探討。 本研究彙整了最近八年(2002~2009)在台灣的晚疫病田間試驗資料，分別為農試所、種苗場、台中改良場埔里分場與亞蔬中心所蒐集之資料，一共30組皆未噴灑殺菌劑之病害數據，透過這些數據分析，找尋氣象因子如何影響晚疫病的發生與流行。 有關氣象因子對晚疫病發生的影響，可在種植期間分為兩部分做探討，第一部份是探討在未發病前，氣象因子對晚疫病發生的影響，透過溫度、相對濕度及雨量的觀測，來瞭解在台灣的氣候型態上，會爆發晚疫病的風險高低，從本研究得知降雨與否是影響晚疫病爆發的重要關鍵，且在降雨期間之平均溫度仍須維持在大約15℃~25℃之間。第二部分是在田間已經發生疫情時，透過氣象因子探討在哪些氣象條件下，有利於晚疫病的擴展與蔓延，本研究使用平滑曲線來觀察氣象因子對病勢進展上升幅度的趨勢，並利用廣義加法模式檢定氣象因子對病勢進展的效應情形，分析後認為溫度與相對濕度對晚疫病之蔓延有顯著的效應，且溫度在15℃下病原菌擴散之速率並不亞於15℃之情況，與發病前所需之溫度條件相較，顯示在病勢蔓延上所需的溫度條件範圍較寬鬆。

Late blight, one of major crop diseases in the world, is caused by Phytophthora infestans (Mont.) de Bary and is harmful to tomato and potato. Usually, Taiwan is not suitable for the occurrence of late blight owing to high average temperature. However, the emergence of new strain in 1998 lead to late blight to become one of the major diseases of tomato and potato in Taiwan. According to literatures, weather factors often have great impact on the occurrence of late blight. The climate in Taiwan is usually not apt to the occurrence of late blight, which mainly occurs in the temperature zone. After 1998, the new strain resulted in the large-scale epidemic. It is presumable that the influence of the weather factors for the new strain is different from that of the old one. Thus, it is necessary to investigate the impact of weather on late blight for different weather situation, especially in sub-tropical monsoon climate of Taiwan. In this study, we have collected recent eight years (2002~2009) field test data of late blight from Taiwan Agricultural Research Institute, Taiwan Seed Improvement and Propagation Station, Pu-Li Branch of Taichung District Agricultural Improvement Station, and Asian Vegetable Research and Development Center (AVRDC). By analyzing the weather factors, we try to find out how the relevant variable affect the outbreak of late blight and its spreading rate. We have divided the analysis into two parts. The first part focuses on the influence of weather factors to late blight before the disease onset. By temperature, relative humidity, and rainfall, we investigated and evaluated the risk factors of the disease outbreak for the conditions of Taiwan's climate. The conclusion of the part is that the rainfall has great impact on the outbreak of late blight, and the average temperature should be in the range of 15℃~25℃. The second part is to figure out how the weather factors accelerate or inhibit the spreading of disease after the disease onset. Smooth curves were used in this study to observe the progress of disease versus the weather factors and generalized additive model were performed to account for the progress. We obtained that the temperature and relative moisture have obvious effect on the spreading of late blight. Moreover, the expanding rate of pathogen when the temperature is less than 15℃ than that when the temperature equals to15℃. In addition, it appears that there is a larger range of the temperature after the disease onset.