放射線菌及常用藥劑應用於樹木褐根病防治之研究

Abstract

褐根病菌(Phellinus noxius)所造成的樹木褐根病為亞洲、非洲、大洋洲及澳洲的熱帶及亞熱帶地區常見之林木根部病害。近年台灣的一些重要經濟果樹或是行道樹等經常發生黃化萎凋甚至急速立枯等情形，多以褐根病菌為主要原因。目前對於褐根病之防治方法以化學防治為主，國外曾報導三得芬、平克座及三泰隆可有效抑制其菌絲的生長，而國內之農試所則發現普克利、4-4式波爾多液、三泰芬、三得芬、撲克拉、滅普寧、佈生、依普同及Pyriferox+40% Quinolate對抑制褐根病菌菌絲有良好的效果。關於生物防治方面，國外曾有報導土壤根圈中的放射線菌(Actinomycetes)及 Trichoderma spp.可以抑制褐根病菌菌絲之生長，但是並無進一步的試驗應用。本研究因此自苗栗、台北及花蓮等地分離出二十株對褐根病菌具有拮抗能力之放射線菌，最後從其中選出兩株效果最好之菌株BR-br及BR-wh，並經定序後對照NCBI資料庫，確認為Streptomyces屬之放射線菌，與本實驗室前人從花蓮玉里之水稻田所分得之放射線菌YU01進行後續之模擬殘根試驗。模擬殘根試驗分成生長箱試驗組及田間試驗組，分別以褐根病菌接種後枝條的乾重損失率及褐根病菌在枝條中的殘存率來評估放射線菌的抑菌效果。結果顯示在枝條放置前七天施用一倍放射線菌培養液的狀態下，枝條的乾重損失率均較對照組少；而在生長箱試驗中枝條的褐根菌殘存率則較對照組低，但在田間試驗中則無。化學藥劑防治方面，本研究篩選測試6種殺菌劑，確定以普克利、待克利及待普克利具有良好抑制褐根病菌之藥效，本實驗另利用莖部注射的方式，將藥劑(50%待普克利乳劑)稀釋100倍後注射至試驗榕樹及垂榕，之後探討藥劑在植株中的分布狀況。結果顯示在注射藥劑5天、10天及15天後，於試驗植株的注射點下方30公分處能測得普克利及待克利。最後測量褐根病菌在不同污染環境處理之殘存率，結果顯示褐根病菌在尿素、大花咸豐草及高麗菜之處理中殘存率較低，其中以在第8天時即能使殘存率降到0%的尿素效果最好。以往防治褐根病時需要大面積的將化學藥劑施用於土壤中，本研究希望藉由生物防治及藥劑注射的方式，降低化學藥劑對人畜環境等所造成的影響。

Brown root rot disease caused by Phellinus noxius is a common root disease distributed in tropical and subtropical regions of Asia, Africa, Oceania and Australia. In recent years, wilting and decline found on some important fruit and urban trees in Taiwan were attributed to this brown root rot disease. At present, the main method to control the brown root rot disease is chemical control. it was a reported that tridemorph, penconazole and triadimenol could inhibit the mycelial growth of Phellinus noxius in foreign country. Taiwan Agricultural Research Institute also reported that 4-4 Bordeaux mixture, propiconazole, triadimefon, tridemorph, prochloraz, mepronil, benthiazole, iprodione and pyriferox+40% quinolate showed good effect to inhibit mycelial growth of pathogen. For biological control, some actinomycetes and Trichoderma spp. from rhizosphere were reported to inhibit mycelial growth of Phellinus noxius, but there was no further application test. In the study, therefore, we isolated 20 strains of actinomycetes showing ability to antagonize Phellinus noxius from Miaoli, Taipei and Hualien. Two strains Br-br and Br-wh with another strain YU01 isolated from Yuli, Hualien were selected to process the simulated stem section test. And depends on the database of NCBI, strains BR-br and BR-wh belong to genus Streptomyces. The dry weight loss rate of inoculated stem section and the survival rate of P. noxius in stem section were used to estimate the antagonistic effect of three actinomycete strains. Results show that the dry weight loss rate of treated stem section are lower than the control in both growth chamber and field test after the treatment of actinomycetes liquid culture. The survival rate of pathogen in treated stem section is also lower than the control one in growth chamber but no significant differences in the field test. In chemical control, we test six fungicide to screen the effective control chemical for brown root rot pathogen. Results show that propiconazole, difenoconazole and difenoconazole+propiconazole show good inhibition effects on the pathogen. This study used fungicide(50% propiconazole+difenoconazole EC 100X) to inject into Ficus microcarpa and Ficus benjamina and determine the distribution of both fungicide inside the tree body. Results show that propiconazole and difenoconazole is existing in the 30 cm point below the injected site on 5th,10th and 15th day. In the last of this study, we test the survival rate of pathogen under different pollution treatments within 10 days. Results show that treatments of urea, Bidens pilosa var. radiate and cabbage can reduce the survival rate of pathogen, especially urea, which can lead to the 0% of survival rate of pathogen after 8th day.To avoid using large amount of fungicide, we expect to reduce the impact of fungicide on the environment by using biological control and trunk injection methods in controlling this disease.