Preliminary Study On The Control Effect Of Cortex Dictamni Extract And Tricyclazole Combination To Rice Blast

Rice blast is one of the three most widespread of destructive fungal disease worldwide.It is very common and serious.The average of reduced output is about 10 to 20 percent of normal yield and the highest one could be more than 50 percent of normal yield.Panicle blast turns rice white and causes no yield in severe case.A new wettable powder(WP)combined by tricyclazole(T.)and self-made cortex dictamni(CD.)was studied on rice blast.The main contents and results are as follows.The toxicity assays of T.and C.D.on rice blast were carried out with mycelium growth rate method.The results revealed that the EC₅₀of T.and C.D.on rice blast were 0.08 mg/ml and 8.85 mg/ml.The combination of T.and C.D.with 9 different ratios was evaluated by the co-toxicity coefficient method.The results showed that they have a quite good synergism prospective.The combination of T.and C.D.with eighteen to two had the highest co-toxicity coefficient and thus the optimal combination was determined.On a basis of the optimal combination and ratio,the optimal prescription of the 20%T.-C.D.WP was described as follows:18%T. (mass fraction,same as follows),2%CD.,1.5%nekal BX,1.5%sodium dodecyl sulfate,4%polyethylene glycol,2%silica,then add the bentonite to 100%.The 20%T.-C.D.WP had high spore germination inhibition of rice blast.The 20%T.-C.D.WP also inhibited melanin synthesis.With the 20%T.-C.D.WP,the rice seed can not be infected.The activities of peroxidase and phenylalanine ammonia-lyase of rice leaf were improved with 20%T.-C.D.WP treatment, which indicated that the 20%T.-C.D.WP could induce rice defense response and improve rice resistance against fungal pathogens.Controlling effect test of 20%T.-C.D.WP was carried out in the field.The results indicated that the control effect of 20%T.-C.D.was obviously higher than that of tricyclazole WP(75%)and wenwenling at 800X concentration of the compound.Based on the control effect test in the field,the application concentration of the compound in the field should be 800 X～1000 X(38 g/mu～47g/mu).