Toxicity of 26 Fungicides against and Synergistic Effects of Binary Mixtures on Oidium heveae

[Objective] This study was conducted to determine the toxicity of 26 fungicides against Oidium heveae and the synergistic effects of their binary mixtures.[Method] The sensitivity of O.heveae to 26 fungicides was determined in vitro and in vivo by calculating EC50 values.Horsfall＇s toxicity rate was preliminarily employed to predict the type of joint action of 180 two-way mixtures,based on which the interaction level of the potentially synergistic mixtures was validated by Sun and Johnson＇s co-toxicity coefficient.[Result] Triflumizole,pyraoxystrobin,flufenoxystrobin,epoxiconazole,pyrametostrobin,flusilazole,pyraclostrobin and tetraconazole were the most potent inhibitors of both spore germination and mycelial growth.An ‘in vitro-in vivo＇ integrated strategy is proposed for screening the inhibitors of O.heveae,according to the fact that data obtained in germination experiment are able to reflect to some extent the effectiveness of fungicide confirmed by pot experiment.Results achieved by Horsfall＇s were in line with that validated by Sun and Johnson＇s,the Horsfall＇s seems to be a convenient means to assess rapidly the potential interaction type and level of fungicides in a binary mixture.Nineteen mixtures interact synergistically：epoxiconazole ＋ pyraclostrobin at the mixing ratio of 6：4,8：2;tetraconazole ＋ flufenoxystrobin at 1：9,2：8,3：7 and 4：6;triadimefon ＋ flufenoxystrobin at 9：1;triflumizole ＋ flufenoxystrobin at 8：2;flusilazole ＋pyrametostrobin at 7：3,8：2 and 9：1;tetraconazole ＋ pyrametostrobin at 6：4;triadimefon ＋ pyrametostrobin at 5：5,8：2;triflumizole ＋ pyrametostrobin at 7：3,8：2;tetraconazole ＋ pyraoxystrobin at 9：1;triflumizole ＋ pyraoxystrobin at 8：2,9：1.[Conclusion] The single fungicides and their binary mixtures are expected to serve as the alternatives to triadimefon and the alternate use of them could delay the buildup of resistant O.heveae isolate.

Toxicity Test of Wood Vinegar Mixed with Different Fungicides on Rhizoctonia solani

There are few kinds of fungicides for the prevention and treatment of Rhizoctonia solani,and the excessive use of chemical fungicides can cause many hazards and toxic and side effects,not in line with the requirements of rice planting. The mixed use of wood vinegar and chemical fungicides can reduce the use of chemical fungicides,alleviate pollution and improve rice quality. In this experiment,the Horsfall method was used to study the synergistic inhibiting effect of mixture between wood vinegar and chemical fungicides on the growth of Rhizoctonia solani,as well as the optimal ratio. The results showed that when wood vinegar was mixed with Captan,the synergistic mixture ratio was 4∶6,3∶ 7 or 1∶ 9,and the toxicity ratio under mixture ratio of 4∶ 6 and 1∶ 9 was 1. 75 and 1. 99,respectively,with significant synergistic effect;when wood vinegar was mixed with Chlorothalonil,the toxicity ratio(1. 08) under mixture ratio of 8∶ 2 was greater than 1,showing additive effect.