(28(1):7-16)The relation between sheath rot and the sterility of rice plant

自典型病斑所獲菌株之最適生長溫度為32℃ ，自葉鞘褐變部位所獲菌株之最適溫度為30℃ ，由此推測稻葉鞘腐敗病菌之生長最適溫度約在30~32℃ 之問。 水稻受傷痍時其感染率可達88 %以上，而無傷痍稻株頗難被感染。又稻細蟎體、脫皮或卵上附著甚多的葉鞘腐敗病菌的分生胞子，因此稻株受稻細蟎加害時，亦容易引起該病害之發生。 稻葉鞘腐敗病比稻細蟎對水稻不稔之影響較大。稻品種在自然環境下，被感染葉鞘腐敗病之程度，稉稻群比秈稻群內之感病品種較多。 十八種殺菌劑中，以抑制圈法測定對病原菌之抑制效果，較佳者有30% Busan，48% ZO-1001，40% Benlate-T , 50% Benlate 及50% Bavistin 等。如以綿線法測定，以30 % Busan，50% Bavistin 及53% Bavistin Combi 等之殺菌效果較佳。 Sheath rot disease of rice caused by Sarocladium oryzae ( Saw.) W. Gams & D. Hawksw. ( Acrocylindrium oryzae Sawada ) is widespread in southern part of Taiwan in recent years . The relation of sheath rot disease to rice sterility is not clear so far, but the disease has become an important rice disease. According to the experiment, the fungus had a wide temperature range for growth. Test of 3 isolates ( AO-1 and AO-2 were isolated from brown tissues of rice sheath , AO-3 was from typical lesion of sheath rot ) indicated that the favorable temperature for growth of AO-1 and AO-2 was at 30℃ and for AO-3 was at 32℃. Wounding was an important factor for pathogen to get infection. Rice plants inoculated by wounding gave high percentage of infection, while it was difficult to get infection without wounding . Because lots of tarsonemid mite, Steneotarsonemus spinki Smiley, carried the conidia of sheath rot fungus, rice plants injured by tarsonemid mite were usually accompanying with sheath rot disease. Experimental data indicated that the effect of sheath rot disease seemed to play an important role on rice sterility than tarsonemid mite. Under nature condition, rice varietes of japonica type are more susceptible than indica type to sheath rot disease. Screen tests of 18 fungicides to the pathogen were carried out by using clearing zone and cotton-string methods. It was found the effective fungicides were 45% Bavistin-combi , 30% Busan, 50% Benlate , 48% ZO-1001, 40% Benlate-T and 65% Bavistin C-65