Groth D E, Bond J A
Professor.
Assistant Professor, Rice Research Station, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, 1373 Caffey Road, Rayne, LA 70578.
Plant Dis. 2006 Aug;90(8):1073-1076. doi: 10.1094/PD-90-1073.
The lack of sheath blight-resistant cultivars requires rice (Oryza sativa) farmers to use fungicides to control the disease and avoid significant reductions in grain and milling yield. Sheath blight (Rhizoctonia solani) epidemics can begin over a period of weeks during the growing season, and initiation date can have significant effects on crop damage and fungicide application timing. Studies were conducted to determine how different epidemic initiation and azoxystrobin application timings affect disease development, rice yield, and milling quality. Sheath blight epidemics in field plots were initiated by inoculation at the green ring (GR), panicle differentiation (PD), early boot (EB), and late boot (LB) growth stages in 2002 to 2004. Azoxystrobin was applied to the foliage at 0.17 kg a.i. ha at 7 days after PD (PD+7), midboot (B), and 50% heading (H). Inoculation significantly increased sheath blight severity and incidence and reduced yield and milling quality. There were no significant effects of inoculation timing at the GR, PD, EB, and LB growth stages. Fungicide applications made between PD+7 and H reduced sheath blight severity and incidence, resulting in higher yield and head rice milling yield compared with inoculated but nonsprayed plots.
缺乏抗纹枯病的品种使得水稻（Oryza sativa）种植户不得不使用杀菌剂来控制该病，以避免谷物产量和碾米产量大幅下降。纹枯病（Rhizoctonia solani）疫情可能在生长季节的数周内开始，发病起始日期会对作物损害和杀菌剂施用时间产生重大影响。开展了多项研究，以确定不同的疫情起始时间和嘧菌酯施用时间如何影响病害发展、水稻产量和碾米品质。2002年至2004年，通过在绿环期（GR）、幼穗分化期（PD）、孕穗初期（EB）和孕穗后期（LB）生长阶段接种，引发田间小区的纹枯病疫情。在幼穗分化期后7天（PD+7）、孕穗中期（B）和抽穗50%（H）时，以0.17千克有效成分/公顷的剂量将嘧菌酯施用于叶片。接种显著增加了纹枯病的严重程度和发病率，并降低了产量和碾米品质。在绿环期、幼穗分化期、孕穗初期和孕穗后期生长阶段接种，接种时间没有显著影响。在幼穗分化期后7天至抽穗50%之间施用杀菌剂降低了纹枯病的严重程度和发病率，与接种但未喷施的小区相比，产量和整精米率更高。
