Control Effect And Screening Of Several Pesticide Against Rhizoctonia Solani

Rhizoctonia solani was known as moire and was one of the three major rice diseases. Currently, the occurrence of Rhizoctonia solani was control by Jinggangmycin, but Jinggangmycin was high dose applied for a long time, and was able to be resisted by the pathogen. The different mixtures of pesticides by re-screening were not only control the occurrence of disease, but also can delay the bacteria resistance. The tebuconazole,dimetachloneand and its active compound on the toxicity of Rhizoctonia solani were tested in vitro and field condition in this paper. Using growth rate methods and field investigation, the depression effect of many single-doses and its compound against Rhizoctonia solani were tested. Finally, the best compound ratio was obtained through the combination of single-doses with high toxicity. Meanwhile many field trials were designed to screen new control and provide a scientific basis to resistance management of rice sheath blight fungicides. The results were as follows:1 Determination of several fungicides toxicityUsing growth rate methods, the toxicity of five fungicides were assayed against Rhizoctonia solani. The results showed that the five fungicides toxicity against Rhizoctonia solani from high to low were 50% Thiram WP>80% Tebuconazole WP>40% Dimetachlone WP>37% Difenoconazole WP>20% Jinggangmycin WP> 25% Triadimefon WP, respectively.2 The best ratio of several fungicidesThe 80% Tebuconazole WP was mixed with 40% Dimetachlone WP. The synergic inhibitory effects of fungicides were evaluated by experimental design of Horsfan virulence. The results indicated that the mixture of 80% Tebuconazole WP and 40% Dimetachlone WP had a synergic effect. The toxicity reached to 94.7% when the mixture ratio was 60:40 and 50:50, obviously higher than the toxicity of single-dose. In addition, the mixture 80% Tebuconazole WP and 40% Dimetachlone WP also demonstrated synergy. The toxicity was 93.46% when the mixture ratio was 50:50. Additionally, different mixture ratio of 80% Tebuconazole WP and 40% Dimetachlone WP showed depression effect of at least 75%, indicating that A168 antibacterial substance could enhance the virulence.3 Field control effectThe 80%Tebuconazole WP.40%Dimetachlone WP,20% Jinggangmycin WP and its mixtures were tested in the rice field intensively infected by Rhizoctonia solani. The results showed that the compound of 80%Tebuconazole WP with 40%Dimetachlone WP with the ration of 60:40 had a high control effect on Rhizoctonia solani, reached up to 82.89%, significantly higher than the compound of 80%Tebuconazole WP with 40%Dimetachlone WP with the ratio of 50:50 carbendazim WP. Meanwhile, both of these compound fungicides were obviously higher than their single-dose. Therefore, the control effects of the other treatments from high to low are as follows: 80%Tebuconazole WP> 20% Jinggangmycin WP> 40%Dimetachlone WP. Variance analysis showed that different treatments had a significant difference. Above all, the different treatment had a most significantly difference. The active compound of Tebuconazole WP and 40%Dimetachlone WP differences between the three treatments was also highly significant.