- 學位論文
台灣水稻飛蝨類害蟲整合管理之新進徑
New approaches to the integrated management of the rice planthopper guild in Taiwan
摘要
褐飛蝨 (Nilaparvata lugens (Stal))、白背飛蝨 (Sogatella furcifera (Horvath)) 及斑飛蝨 (Laodelphax striatellus (Fallen)) 為東亞地區水稻重要害蟲。在台灣，褐飛蝨及白背飛蝨以少量族群越冬，海外遷入蟲源成為造成台灣水稻嚴重受害之主要來源。遷入蟲源之特性，包含害蟲種類間之發生比例、生物小種及抗藥性等，將深深影響到台灣蟲害管理策略之擬定。 利用回溯軌跡系統 (backward trajectory analysis)，分析1990~2005年間高空捕網及誘蟲燈所捕獲蟲體之資料，並顧及遷出時期及氣候等條件，推斷台灣之褐飛蝨及白背飛蝨遷入來源，結果顯示中國華南地區、越南及菲律賓呂宋島為可能遷出源，其中又以中國華南為最主要地區。在第一及第二期作水稻遷入蟲源來自中國華南地區，分別有77% (內含48%源自越南) 及65% (內含50%源自越南)；有37% 及56% 來自越南。颱風為自海外引入大量蟲源之最主要因子。 為了解在台灣四個水稻主要栽培地區褐飛蝨及白背飛蝨族群之可能遷出來源，本研究利用於2008~2009年採集褐飛蝨及白背飛蝨族群，其粒線體DNA片段 (cox1 + trnL2 + cox2) 序列 (分別為1928及1927 bp) 作為分子標誌進行定序分析，結果顯示褐飛蝨及白背飛蝨同種內各族群個體間之遺傳距離相當接近，僅在特定年份之特定地區，有少數個體可被歸類成另一族群。是故，以目前所利用之分子標示，尚無法得知台灣各地區之褐飛蝨及白背飛蝨族群之來源。 為了解遷入台灣之褐飛蝨族群對抗性水稻品種之衝擊，在2007~2010年檢測台灣四個不同地區褐飛蝨族群，於Mudgo (具Bph1抗性基因)、H105 (具bph2抗性基因)、Rathuheenati (具Bph3及Bph17抗性基因) 及Babawee (具bph4抗性基因) 等四個具不同抗性基因水稻品種上，接入剛羽化之短翅型雌成蟲，以雌蟲腹部可膨大或能存活超過5日者，視為具有為害能力，結果顯示各地區褐飛蝨族群在Mudgo及H105等抗性水稻品種上，75~100% 雌蟲能存活超過5日者，其中有65~100% 雌蟲腹部可膨大；在Babawee抗性水稻品種上，30~83% 雌蟲能存活超過5日，其中有3~28% 雌蟲腹部可膨大，且近年來有逐漸增加之趨勢；在Rathuheenati抗性水稻品種上，20~80% 雌蟲能存活5日，其中有0~28% 雌蟲腹部可膨大。此結果顯示抗褐飛蝨之水稻基因Bph1及bph2由於相對應生物小種之出現而崩潰，近幾年來已顯示抗性基因bph4也逐漸失去效力。是故，積極引入不同抗性基因於水稻育種系統，以因應褐飛蝨生物小種在台灣發生之現況，乃為當務之急。 此外，在2007-2010年間利用局部點滴法，檢定台灣四個地區之水稻三種飛蝨族群對藥劑之感受性，半數致死劑量 (LD50) 結果顯示褐飛蝨對芬普尼 (fipronil) 及達特南 (dinotefuran) 兩種藥劑之LD50甚低，分別在0.10~1.25及0.09~2.70 μg g-1之間；但益達胺 (imidacloprid) 之檢定結果較高，LD50 為35.8~53.4 μg g-1，且近期有逐漸上升之趨勢。白背飛蝨族群對賽速安 (thiamethoxam)、益達胺及達特南等三種藥劑之LD50甚低，分別在0.06~2.72, 0.05~1.73及0.12~3.05 μg g-1之間；但芬普尼之檢定結果較高，LD50 介於2.67~13.7 μg g-1，且近期有逐漸上升之趨勢。斑飛蝨族群對芬普尼之LD50最低，介於0.04~0.74 μg g-1，惟各地區檢測各種藥劑感受性之結果，依年度及地區之變化相當大。褐飛蝨族群對賽速安及益達胺藥劑感受性之檢定結果，呈現正交互抗性(positive cross-resistance) 之關係。褐飛蝨及白背飛蝨分別對益達安及芬普尼之藥劑感受性調查呈現明顯差異現象。依目前檢定之結果，並未有一種能同時防治三種飛蝨之藥劑，只有達特南對褐飛蝨及白背飛蝨仍具有良好防治效果。 為簡化水稻飛蝨類害蟲之管理工作，本研究利用共食群 (feeding guild) 之概念，建立水稻三種飛蝨的為害當量系統 (injury equivalency system)，此系統可整合同一共食群中，不同種類各發育期之為害，可更精確估算其對水稻之為害量，也可用於預測同一為害群中，不同害蟲種類之各蟲期混棲為害時，對水稻產量造成之可能損失，並建立因應多種經濟變因情況下的水稻飛蝨類經濟為害限界矩陣，此系統之提出為改善水稻害蟲整合性管理決策擬定 (decision-making) 之第一步，可供未來推廣應用及改進。 為配合共食群經濟防治基準之應用，本研究亦探討其最適取樣技術，將三種水稻飛蝨整合成一複合群 (rice planthopper complex)，比較各別物種飛蝨與三種飛蝨複合種族群之空間分布型式，結果顯示除白背飛蝨外，其餘均呈現聚集型分布。經由Taylor’s power law分析褐飛蝨、白背飛蝨及斑飛蝨在族群密度為每叢水稻上10隻之最適取樣數，分別為155、54及380叢；但以三種飛蝨複合種之最適取樣數則為115叢水稻，大幅減輕取樣工作之負荷。 綜觀上述得知，台灣水稻飛蝨遷入源頭主要為中國華南地區、越南及菲律賓呂宋島，然而利用粒線體DNA片段作為分子標誌，尚無法有效區分台灣各地區之褐飛蝨及白背飛蝨族群內之個體差異，是故，目前無法得知各地區蟲源之確切來源。檢定褐飛蝨生物小種及三種飛蝨之藥劑感受性，所得結果提供了管理技術擬定之重要資訊。利用共食群之概念，建立三種水稻飛蝨共同經濟為害基準及最適取樣數，以簡化水稻飛蝨類害蟲防治與否之決定，可作為未來改善台灣水稻害蟲管理系統之基礎。
並列摘要
The brown planthopper (Nilaparvata lugens (Stal)), white-backed planthopper (Sogatella furcifera (Horvath)) and smaller brown planthopper (Laodelphax striatellus (Fallen)) are the most important sucking pests of rice (Oryza sativa) in East Asia. Evidence showed that the overwintering populations of both brown planthopper and whitebacked planthopper in Taiwan were very low. The major source for causing serious damage to the rice crop was the immigrants from overseas. The characters of the immigrants, including the relative numbers of the pest species, biotypes and insecticide resistance, could deeply affect the management strategy of the pests. Therefore, we conducted experiments to monitor and make sure the source of their immigration and understand the characters of the immigrants in order to improve their population management on rice. First of all, the trap catch data of the planthoppers from 1990 to 2005 were analysed by the backward trajectory method to figure out the most likely source of the immigrant planthoppers taking into account the emigration periods and weather conditions. It showed that southern China, Vietnam and the Philippines (Luzon Island) were the possible source areas. Southern China especially was the most important source of emigration. Of all the immigration cases tested, the sources from southern China were estimated to be about 77 % (including 48% from Vietnam) in the first rice crop and 62 % (including 50% from Vietnam) in the second rice crop. Vietnam came second with about 37% and 56% in the first and second rice crop, respectively. Typhoon was the most important weather factor inducing mass emigrations from overseas. In order to pin-point the destination of the immigrants from different sources, brown planthopper and whitebacked planthopper samples were collected from four districts of rice cultivations in Taiwan during 2007-2008. A total of 1928 and 1927 base pair region of mitochondrial DNA (co1 + trnL2 + co2) for brown planthopper and whitebacked planthopper were sequenced. The results showed that the genetic distance within their populations of either pest was very close, though a few samples from a particular year and locations could be classified into different groups. The genetic markers failed to distinguish among populations collected from different years and locations in Taiwan. Bioassay tests were conducted during 2007-2010 to figure out the possible existence of any biotype of the brown planthoppers collected from the four districts. Four indicator rice varieties with different resistant genes were tested to differentiate the biotype. They were Mudgo (carrying a resistant gene Bph1), H105 (carrying a resistant gene bph2), Rathuheenati (carrying two resistant genes Bph3 and Bph17), and Babawee (carrying a resistant gene bph4). The newly emerged brachypterous females of brown planthopper from each district were released onto each biotype indicator rice plants. Females with significant swollen abdomen or survived for more than five days were considered as virulent. Results indicated that the varieties with resistant genes Bph1 and bph2 had been broken down by the biotypes, and the resistant varieties with bph4 might become ineffective to the brown planthopper in near future. Breeding varieties with new resistant genes to cope with the virulent biotypes of brown planthopper is urgently needed in Taiwan. Toxicity of four commonly used insecticides to local population of the three rice planthoppers from these districts was run by topical application during 2007-2010. It showed that the LD50 value of fipronil to brown planthopper was 0.10~1.25 μg g-1, and that of dinotefuran was 0.09~2.70 μg g-1, while imidacloprid was significantly high (35.8~53.4 μg g-1). As to whitebacked planthopper, thiamethoxam (0.06~2.72 μg g-1), imidacloprid (0.05~1.73 μg g-1) and dinotefuran (0.12~3.05 μg g-1) were all low, except fipronil (3.67~13.7 μg g-1). As to smaller brown planthopper, LD50 of fipronil was 0.04~0.74 μg g-1 while other insecticides tested were variable depending on the locations. The bioassay also showed a positive cross-resistance between imidacloprid and thiamethoxam existed in tests to the brown planthopper. These tests showed that no single insecticide could be used to effectively control the three species of the planthoppers, and only dinotefuran remains effective for controlling both brown and whitebacked planthoppers. Based on the concept of an injury guild, and injury equivalency derived from the relative amount of stage specific honeydew excretion, a common economic injury level (EIL) was established for the rice planthopper guild composed of the three species of planthoppers. A matrix of economic thresholds (ETs) established and incorporating changes of management cost and rice price was employed and served as a control decision guide for the guild samples. This common EIL greatly improved the decision-making of the pest management in rice as far as multiple pest species is concerned. A sampling technique to facilitate the decision-making of the common EIL was also developed for the injury guild via Taylor’s power law and the estimation of the optimal sample size to monitor the pest populations in the rice fields. All planthopper counts disregard the species were pooled into a rice planthopper complex based on the concept of injury guild to enable further analysis. Finally, I conclude that southern China, Vietnam and the Philippines (Luzon Island) were the most likely sources of emigration areas of the brown planthopper and whitebacked planthopper in Taiwan. However, the genetic marker of mtDNA failed to distinguish among populations from the major rice cropping areas in Taiwan. Bioassay of the biotypes of brown planthopper and the insecticide susceptibility of three rice planthoppers provided the essential information for the management of the planthoppers. And the establishment of the common economic injury level and optimal sample size of these three species of rice planthopper based on the concept of feeding guild greatly simplified the sampling and decision-making for the control of these pests.