水稻秧苗立枯病病因之研究

Abstract

本研究係探求早秧田新病害秧苗立枯病之病因及其防治方法為目的。本年度所得結果簡述如下： 自各地採集被害病株經分別分離菌類，鑑定結果有Fusarium moniliforme、F. oxysporum、F. solani、 Curvularia lunata、 Corticium rolfsii、 Scierotium hydrophilum、 Rhizoc-tonia solani (=Pellicularia sasakii)、 Pythium sp.、 Monilia sp.等。此等菌類經單獨接種於土壤中，測定病原性結果，以C. rolfsii之病原性最強，其次為Pythium sp.；再其次為R. solani及S. hydrophilum。但Fusarium與C. lunata兩種菌亦不可忽視。如果二種菌類混台接種時，無論何種菌與C. rolfsii混合其病原性皆呈最強，其他菌類混合與否對病原性無多大變化。試驗結果顯示稻苗立枯病之發生與土壤有密切關係，故土壤處理將有助於立枯病之防治。 稻種子（臺南5號）上附看菌類，經鑑定結果以Fusarium與Curvularia兩種菌之出現頻度最高，其次為Monilia、 Cochliobolus、 Brachysporium等菌，再其次為Penicillium Pyricularia等兩種菌，Alternaria與Aspergilus兩種菌之出現頻度不多。故欲預防秧苗立枯病之發生，稻種徹底消毒係極重要步驟之一。 藥劑防治可應用Tachigaren（每箱0.5撮）或Orthocide（每箱1公克）稀擇液於播種後即澆灑，頗有效；另利用Chloropicrin行土壤燻蒸消毒亦可得良奸效果；利用Foleidin或Orthocide作拌種之效果亦頗佳。 This experiment is aimed at solving the problem for the etiology, ecology, and control of rice seedling blights. A new disease problem so called non-submerged seedling disease was occurred following the new type cultivation of rice seedling by wood box for the mechanization of rice transplanting since 1971. Various fungi were isolated and identified from disease specimen and problem soil collected from different regions. When the fungus inoculated individually into the soil, C. rolfsii was the strongest pathogenicity in virulence to rice seedlings, followed by Pvthium sp., then R. sotani and S. hydrophilum. Besides, Fusariuni sp. and C. lunata could not be negligible, owing to the high frequency of appearance. In case of mixed inoculation with two different fungi, the combination mixed with C. rolfsii usually revealed the strongest pathogenicity in virulence. The other combinations, however, gave little influence on pathogenicity. The results also indicated the occurrence of rice seedling blight was correlated with soil, therefore, soil treatment may account as one way of the disease control. The fungi which adhered to rice seeds were also identified. The data showed that Fusariuni and Curvularia had the highest frequency in appearance followed by Monilia, Cochliobolus, and Brachysporium; then Penicillin in, Pyricularia; the frequency of Alternaria and Aspergilus were very low, It indicated that rice seed treatment was very important for control of the rice seedling blight. As to the chemical control of the rice seedling blight, Tachigaren and Orthocide sprayed at the rate of 0.5 ml and I gram per box respectively gave good control of the dsease. In addition, soil fumigation with Chloropicrin, or rice seed treated with Folcidin or Orthocide could also eliminate the disease.