芝麻棒孢叶斑病的发生规律和高效防治药剂的筛选

Occurrence characteristics and fungicide screening of Corynespora leaf spot in sesame

芝麻棒孢叶斑病是芝麻常发性病害,严重影响着芝麻的产量和品质。为确定芝麻棒孢叶斑病防治的最佳时期,制定有效的药剂防治措施,2017-2019年对黄淮芝麻主产区平舆县的棒孢叶斑病发生情况进行了监测,并测定了16种杀菌剂的室内毒力和田间防效。结果表明,芝麻棒孢叶斑病的发生初期为现蕾期-初花期,病情发展的转折期为初花期-盛花初期(黄淮产区为7月20日-31日,此时田间发病率小于3%或病情指数小于1)。16种供试杀菌剂中己唑醇、咪鲜胺、氟硅唑、戊唑醇、苯醚甲环唑、腐霉利、噻呋酰胺和咯菌腈对芝麻棒孢叶斑病菌的毒力较强,EC_(50)分别为1.5734×10^(-4)、0.1248、0.7128、1.3922、2.0014、2.7323、5.4327、6.1285 mg/L;噻呋酰胺、己唑醇、嘧菌酯、戊唑醇和苯醚甲环唑的田间防效和增产效果较好,防效分别为67.19%、65.86%、61.17%、60.87%、61.83%,增产率分别为38.96%、36.86%、39.72%、34.96%、38.56%;苯醚甲环唑、己唑醇、嘧菌酯和戊唑醇施药2次的防效和增产效果最佳。综合研究结果,芝麻棒孢叶斑病防治的最佳时期为初花期-盛花初期(黄淮产区7月20日-31日),或在田间发病率达到3%或病情指数达到1之前进行防治,建议选择噻呋酰胺、己唑醇、嘧菌酯、戊唑醇和苯醚甲环唑等杀菌剂,同一杀菌剂连续施用次数不超过2次,施药间隔10 d。为减少农药残留和防止病原菌产生抗(耐)药性,不同药剂可交替轮换使用。

Corynespora leaf spot is sesame common disease,seriously affecting the yield and quality of the sesame.To determine the optimal period of prevention and control of Corynespora leaf spot and formulate effective pesticide control measures,the occurrence of Corynespora leaf spot in Pingyu County was monitored from 2017 to 2019.The indoor toxicity and field control efficiency of 16 fungicides were determined.The results showed that the initial occurrence stage of Corynespora leaf spot was the squaring stage-early flowering stage,and the turning stage of disease development was the early flowering stage-full flowering stage(20-31,July,in Huanghuai region,the incidence was less than 3%or the disease index was less than 1).Among the 16 fungicides,hexaconazole,prochloraz,flusilazole,tebuconazole,difenoconazole,procymidone,thiofuramide and fludioxonil were the stronger toxicity to Corynespora leaf spot,EC_(50) is 1.5734×10^(-4),0.1248,0.7128,1.3922,2.0014,2.7323,5.4327 and 6.1285 mg/L.Thiofuramide,hexaconazole,azoxystrobin,tebuconazole and difenoconazole had well field efficacy both on disease control and yield improvement.The control efficacies were 67.19%,65.86%,61.17%,60.87%and 61.83%,the increase rates were 38.96%,36.86%,39.72%,34.96%and 38.56%,respectively.The control efficacy and yield increase efficacy of difenoconazole,hexaconazole,azoxystrobin and tebuconazole were the best when applied twice.According to the results,the optimal control period of Corynespora leaf spot in sesame was from early flowering stage to full flowering stage as 20-31 July in Huanghuai region,or before the disease incidence reached 3%or disease index reached 1.Thus it is supposed to select thiofuramide,hexaconazole,azoxystrobin,tebuconazole and difenoconazole as fungicides.The same fungicide should not be applied for more than twice with an interval of 10 days.In order to reduce fungicide residues and prevent pathogens from producing resistance(tolerance),different fungicides could be used alternately.