(20(1):61-66)RE-EVALUATION OF MERCURIC FUNGICIDES FOR RICE SEED TREATMENT

本試驗為重新測定Riogen片劑與Granosan M水和劑等現行推廣之有機汞劑之稻種消毒藥效而舉行。試驗分為穀粒法與綿線法。供試濃度為惟廣使用濃度。茲簡述本次試驗結果如下： (一) 穀粒法試驗中，病原菌培養於殺菌後之穀粒上時，由於菌絲伸展至穀粒內部影響藥劑之消毒效果。因此以Riogen片劑處理8小時始完全抑制P. oryzae之生長，對於G. fujikuroi則只有96%之效果。Granosan M 水和劑略優，處理2小時即可完全殺死P. oryzae，對G. fujikuroi則需7小時始達100%之藥效。 (二) 綿線法中除Riogen片劑2,000倍處理G. fujikuroi之效果為98%外，其餘處理均有100%之殺菌效果。 (三) Riogen片劑與Granosan M水和劑之藥效，在 10~25℃之問時，溫度愈高藥效愈顯著。 (四) 總之，在供試之兩種藥劑中Granosan M水和劑對P. oryzae及G. fujikuroi之制菌力均較Riogen片劑略優，即使將Riogen片劑之濃度加倍其藥效仍較Granosan M水和劑稍差；但其差異並不顯著，故Riogen片劑仍不失為一種優良之種子消毒劑。若就病原菌言之，則兩種藥劑對於P. oryzae之殺菌效果均要比G. fujikuroi為高。 The present experiment compared the effectiveness of two organomercuric compounds, Granosan M wp. And Riogen tablet, as seed-treatment for controlling two major rice diseases, rice elongation caused by Gibberella fujikuroi. (Saw.) Wr. And blast caused by Pyricularia oryzae Cav. Two different methods, namely, the rice-grain method and cotton-string method were employed. The results obtained are summarized as follows. 1. Growing the test pathogens on autoclaved rice grains, the hyphae penetrated deep into the grains, and rather low percentage of kill was obtained by the rice-grain method. When reated with Riogen tablet at 1:2,000 for 8 hours growth of P. oryzae was completely inhibited while 96% inhibition only was obtained for G. fujikuroi. Granosan M wp. Had a better effect for P. oryzae which was inhibited completely with a 2-hour treatment but G. fujikuroi. needed 7 hours for some degree of control, using in both cases at 1:1,000 dilution of the test compound. 2. By the cotton-string method, all treatments gave a 100% kill, with the exception of Riogen at 1:2000 dilution for 5 minutes on G. fujikuroi. The percentage kill obtained with this treatment was 98%. 3. The killing effect of Riogen and Granosan was influenced by temperature. Whthin the temperature range of 10-25℃, the fungicides were more effective as the test temperature was higher. 4. In this experiment which was carried out in laboratory, Granosan appeared to inhibit the growth of both P. oryzae and G. fujikuroi more than Riogen at the test concentrations, but the difference was not significant. We conclude that Granosan M wp. and Riogen tablet are both valuable in rice seed-treatment for controlling P. oryzae and G. fujikuroi. Either of the two fungicides was more effective on P. oryzae than on G. fujikuroi