Bioactivities of carbendazim, etc. five fungicides against Rhizoctonia solani in tobacco

Bioactivities of five different fungicides (carbendazim, mancozeb, dimethachlon, iprodione and difenoconazole) to Rhizoctonia solani were determined using bioassay methods at the stages of mycelial growth, sclerotium production and germination. And in vivo protective and curative effects of these fungicides against tobacco sore shin on detached leaves were also analyzed. The results showed that the five selected fungicides exhibited different inhibitory activities at all assays. The most effective fungicide against the mycelial growth, sclerotium production and germination of R.solani was carbendazim, with the average mycelial growth EC50 value of (0.06 ±0.01) mg/L, 0.25 and 20 mg/L of carbendazim exhibited 100% inhibition against sclerotium production and germination, respectively. For iprodione, its average EC50 value for mycelial growth was (0.35 ±0.15) mg/L, 2 and 100 mg/L of iprodione exhibited (54.79 ±12.58)% and 100% inhibition against sclerotium production and germination, respectively. For difenoconazole, its average EC50 value was (0.55 ±0.53) mg/L, 5 and 200 mg/L of difenoconazole exhibited (97.97 ±2.64)% and 100% inhibition, respectively. For dimethachlon, its average EC50 value was (1.31 ±0.14) mg/L, 10 and 100 mg/L of difenoconazole all exhibited 100% inhibition. The lowest was detected in the case of mancozeb, with average EC50 value of (6 ±0.20) mg/L, 10 and 100 mg/L of mancozeb exhibited approximately (43.58 ±31.87)% and 0 inhibition, respectively. The most effective fungicides for protective activity were carbendazim, iprodione and dimethachlon (all showed> 99% efficacy at 50 mg/L), followed by mancozeb (75.83%), and the lowest activity was detected in the case of difenoconazole (39.29%). The most effective fungicide for curative activity was carbendazim (50 mg/L exhibited 93.46% efficacy), followed by dimethachlon, iprodione and difenoconazole (all showed> 84% efficacy at 200 mg/L), and lowest activity was observed in the case of mancozeb (exhibited 76.40% efficacy at 800 mg/L). The results have provided scientific evidence and reference for screening fungicides to control tobacco sore shin.