茶樹赤葉枯病之流行病學及非農藥防治

Abstract

茶樹 Camellia sinensis (L.) O. Kuntze 為多年生常綠灌木至小喬木植物，經加工成為嗜好性飲料，因其清香深受國人喜愛而有大量之種植。茶樹病害甚多，其中以炭疽病菌(Colletotrichum gloeosporioides)所造成之茶赤葉枯病最為常見。本研究為調查茶赤葉枯病之流行及所造成之危害並研究防治之道，於北部坪林、文山、楊梅三地區進行病害嚴重度之監測，又因於坪林地區發現到有新芽焦枯之芽枯病產生，經組織塊分離法可得到炭疽病菌(Colletotrichum spp.)與擬盤多毛孢菌(Pestalotiopsis spp.)兩種病原真菌，經柯霍氏準則接種嫩芽確認芽枯病主要由茶赤葉枯病病原菌所造成，而經分生技術鑑定為茶赤葉枯病病原(C. gloeosporioides)。芽枯病於坪林冬天可造成20~50%之新芽焦枯，造成冬茶產量下降甚至無法採收。該病菌在不同溫度下培養發現於25℃菌絲生長最佳，於15℃下生長較差，在35℃下則無法生長。而依據2013年12月至2014年6月流行病學研究調查顯示，該病害於坪林地區月均溫較低、月平均相對溼度較低及月平均風速較大時易發病，且與坪林地區之赤葉枯病有中度至高度正相關，說明赤葉枯病於葉片產生之孢子，可經風雨飛濺至嫩芽。而茶赤葉枯病則是於月平均風速較大時，較易發病，且青心烏龍比台茶十二號、四季春及鐵觀音皆較感病。由於近年非農藥防治逐漸為大眾所青睞，也免除農藥殘留之疑慮，因此選用植物萃取液及拮抗微生物來進行防治試驗。經選用大蒜、薑、薑黃、肉桂、丁香、五味子及藿香等七種植物萃取液進行菌絲生長抑制與孢子發芽抑制試驗，發現酒精萃取之丁香、肉桂及藿香皆具有抑菌效果，然只有薑黃之酒精萃取液及蒜之酒精萃取液(0.2%)於盆栽防治試驗中具抑制芽枯病之效果，其抑制率僅25%。經拮抗菌對峙試驗顯示商品化之枯草桿菌(Bacillus subtilis)與鏈黴菌(Streptomyces sp.)YU01均有抑菌效果，但於盆栽試驗中發現鏈黴菌 YU01於接種前一天施用有83%之抑制率，枯草桿菌則無。而於農藥對芽枯病菌絲生長抑制試驗證實測試之13種藥劑中免賴得、嘉賜貝芬可有效防治此病原菌。而根據接種試驗結果，發現芽枯病菌除青心烏龍外對四季春、臺茶十二號及大葉烏龍等品種皆有病原性，而以芒果炭疽病、草莓炭疽病、咖啡炭疽病等病原菌接種茶樹嫩芽，皆不會造成芽枯。本研究於田間調查、病原性測試結果皆證明茶赤葉枯病單獨感染嫩芽可造成芽枯病，但為何此病徵只於坪林地區發生仍有待進一步之研究。

Tea (Camellia sinensis (L.) O. Kuntze) is a kind of evergreen perennial shrub or small tree, can be processed to the most widely consumed beverage in the world. Due to its fragrant flavor, tea has been massively grown in Taiwan. Tea can be affected by many diseases, among them the tea brown blight disease (Colletotrichum gloeosporioides) is the most common fungus disease in the field. To investigate the severity of tea brown blight disease, and to control it, this study monitored the disease severity of tea brown blight at Pinglin, Wenshan and Yangmei areas. As a new sprout wilt disease was found at Pinglin, New Taipei, tissue isolation methods were conducted to obtain the suspect pathogen. Results showed that both Colletotrichum and Pestalotiopsis can be isolated from the wilting sprout. Through the rules of Koch’s postulates and molecular identification, we confirmed that the sprout wilt is mainly caused by C. gloeosporioides. Sprout wilt disease can cause 20 to 50 percent of yield loss in Pinglin, resulting in severe economic impact on winter tea in Pinglin area. Culturing this pathogen at different temperatures showed that this pathogen grows best at 25℃ and slower at 15℃, but cannot grow at 35℃. Basing on epidemiological study from December 2013 to June 2014, this disease prefer the low temperature, low humidity and high wind speed. The relationship between sprout wilt and tea brown blight disease is generally positively correlated, indicating that the spores from tea leaves with brown blight disease can splash to sprout by wind and rain and cause the disease. On the other hand, brown blight disease occurred more severe in season of high speed wind. As compared to Ttes No.12, Shy Jih Chuen and Tieguanyin, the cultivar Chih Shih Oolong is the most sensitive to brown blight disease. In order to eliminate the concerns of pesticide residues, non-pesticides control of plant disease is right now a favorite by farmer. Therefore we choose seven kind of plant to prepare their extracts and two antagonistic microorganisms to test to control the sprout wilt in this study. They are ginger, turmeric, cinnamon, cloves, cablin potchouli herb and Chinese magnoliavine fruit. The test of their extracts for effect on mycelial growth and spores germination, showed that only ethanol extract of clove, cinnamon and cablin potchouli herb have some inhibition potential against the pathogen. However, only the ethanol extract of turmeric and garlic (0.2%) exhibit the inhibition rate of about 25% in pot plant test. On the other side, antagonism microorganisms Streptomyces (Streptomyces sp.) YU01 and Bacillus subtilis also have inhibition effect on this pathogen in dual culture experiment. Streptomyces YU01 even has 83% inhibition rate to control the sprout wilt disease in pot plant test, when applied one day before the inoculation. Whereas the Bacillus subtilis has no inhibition effect in pot plant test. A total of 13 fungicides were screened for their control rates on tea brown blight pathogen by mycelial growth inhibition test. Results showed that both benomyl, kasugamycin plus carbendazim, have the best potential to control the disease. In this study, we found that the sprout wilt pathogen can infect not only the Chin Shin Oolong cultivar, but also the cultivar Ttes No.12, Shy Jih Chuen and Dah Yeh Oolong. We also found that anthracnose pathogens from mango, strawberry and coffee, cannot cause the tea sprout wilt. Our study proved that the pathogen from brown blight can transmit and cause sprout wilt as shown in our field survey and pathogenicity test. However the reason of sprout wilt only occur in Pinglin area still need further studies in the future.