(27(3):237-244)Epidemiological studies of rice blast disease observations in 1977

民國66年一期作葉稻熱病在臺南5號品種上之發病率為0.03~14.1%•，嘉農秈8號上為0.02~9.6%，穗稻熱病在臺南5號上發病率為2.2~57.9%，嘉農仙8號上為0~74.67%，均視試驗地點而異，二期作無論臺南5號或嘉農仙8號之葉及穗稻熱病發生皆甚輕微。胞子採集數以葉稻熱病發病率較高的地點採集的數目較多，一期作採集的胞子數較二期作多。胞子開始採集得到的日期在葉稻熱病發生之前或後，視地點而異，一期作葉稻熱病發生前7天的日平均溫度大多在20~25℃之間，此溫度對葉稻熱病發生可能很重要。在水稻生育期間胞子採集最多的期間係在發病高峰期以後的初期，一年當中以4月或5月採集的胞子數最多。 During the first crop of 1977, there was a rather low incidence of leaf blast in all locations of observation, ranging from 0.03-14.1% on Tainan 5, and 0.02-9.6% on Chianung-shen 8. The incidence of panicle blast ranged from 2.2-67.9% on Tainan 5 and 0-74.6% on Chia-nung-shen 8. There was also a light occurrence both the leaf and panicle blast on either Tainan 5 or Chia-nung-shen 8 during the second crop. A considerably higher amount of conidia was trapped at the locations where there was a higher disease incidence of leaf blast. Generally, more conidia were trapped in the first crop than in the second crop. The trapping of conidia might either proceed or follow the first appearance of leaf blast during the first crop. The average daily temperature in the seven-day period before the disease first appeared fell in the range of 20-25°C. This temperature range might be an important factor which favored the occurrence of leaf blast. The peak occurrence of conidia in the air did not coincide with the peak incidence of leaf blast but was detected shortly after. More conidia were collected in April or May than other times in the year