(25(3):199-205)FLUCTUATION OF RICE BLAST UNDER DIFFERENT FUNGICIDAL TREATMENTS

葉稻熱病病勢的進展，從病斑出現到罹病程度達到最高峰僅需14天。穗頸稻熱病病勢之進展到最高峰臺南5號僅15天，嘉農秈11號僅9天，故抗病品種病勢進展遲緩，發病率低；感病品種病勢進展迅速，且發病率高。不同藥劑處理區之病勢進展隨對照區病勢之進展而上下，即對照區之病勢上升時藥劑處理區之病勢亦隨著上升，對照區之病勢下降時，藥劑處理區之病勢亦隨看下降，只是藥劑處理區之發病率較對照區低，受害較輕微。 An epidemic of leaf blast on Tainan 5 from the initial outbreak to the highest peak of the disease severity continued for 14 days. The development of neck blast on Tainan 5 and Chia-nung-sen 11 was 15 and 9 days, t respectively. Hence; the development of rice blast was slowly and the disease incidence was ‘slightly on resistant variety while it was rapidly and seriously on susceptible variety. The disease development under different fungicidal treatment plot fluctuated with control plot. In other words, the disease ‘incidence increased in the control plot and the disease incidence in the treatment plot also increased and vice versa