Screening For Controlling Peanut Soilborne Fungal Diseases On Peanut By Seed-coating

Crown rot, root rot and sclerotium blight are three main peanut soilborne fungal diseases in China, caused by Aspergillus niger Van Tiegh,Fusarium solani(Mart)Sacc and Sclerotium rolfsii Sacc, respectively. Those diseases above often occur in different periods during the same growing season and lead to heavy yield losses. Fungicide seed-coating has been widely applicated to control soilborne diseases for its efficiency and convenience. However, few fungicides are registered for controlling three peanut soilborne fungal diseases in China. The objective of this research was to screen safe and high-efficient seed-coating fungicides for controlling the three peanut soilborne fungal diseases by once treatment. In this paper, we screened high activity fungicides against A. niger, F. solani, S. rolfsii in laboratory. And then the safety of eight preparations of fungicide seed-coating at different rates on peanut in the glasshouse condition was determined. The seedling inoculation experiments in a greenhouse and field trials were conducted to investigate the control efficacies of eight preparations of fungicides by seed-coating. The results are as follows:1. The EC50 values of pyraclostrobin, difenoconazole, fluazinam, fludioxonil and triflumizole in inhibiting A. niger were 0.011, 0.054, 6.56, 0.52 and 1.43 mg/L, respectively, which exhibited significant differences. The EC50 values of pyraclostrobin, difenoconazole, fluazinam, fludioxonil and triflumizole in inhibiting F. solani were 0.27, 0.49, 0.31, 0.44 and 0.37 mg/L, respectively, which exhibited high toxic. The EC50 values of pyraclostrobin, difenoconazole, fluazinam, fludioxonil and triflumizole in inhibiting F. solani were 0.19, 1.14, 0.10, 0.47 and 15.33 mg/L, respectively, which exhibited significant differences.2. Peanut seedling emergence and growth were conducted in the safety pre-test at 20 ℃ and 25 ℃, where three varieties of peanuts were seed-coated with difenoconazole FS and CS, triflumizole FS at the rates 50, 100 and 200 g a.i./100 kg seed, fluazinam FS and CS, pyraclostrobin EC and CS at the rates 40, 80 and 160 g a.i./100 kg seed, fludioxonil FS at the rates 20 and 40 g a.i./100 kg seed. Seed-coated with triflumizole FS 200 g a.i./100 kg seed, peanut emergence rate and plant height were decreased, emergence day was delayed 1~2 d, length and fresh weight of root, shoot and leaf fresh weight were not significantly affected. Except for triflumizole FS 200 g a.i./100 kg seed, emergence and seedling growth of other seven fungicides and triflumizole FS 50 and 100 g a.i./100 kg seed seed-coating were not significantly affected, which were relative safe.3. The seedling inoculation experiments using the crown rot, root rot and sclerotium blight pathogens were conducted in a greenhouse. The incidence of peanut crown rot and root rot decreased, and the control efficacies were higher than 79.71%, by seed-coating treatment with eight preparations of fungicides above. The control efficacies seed-coated with difenoconazole FS and CS 200 g a.i./100 kg seed, pyraclostrobin EC and CS 160 g a.i./100 kg seed were the higher,with 90.64%-95.44%. The control efficacies for peanut sclerotium blight were significantly different. Except for pyraclostrobin EC 40 g a.i./100 kg seed and triflumizole FS 50 g a.i./100 kg seed, the control efficacies of other treatments were all higher than 69.62%. The control efficacies of pyraclostrobin CS 160 g a.i./100 kg seed was the highest, with 90.12%.4. The results of field trials indicated that triflumizole FS 100 g a.i./100 kg seed impeded emergence 1-2 d, and not affected the emergence rate. Except for triflumizole FS 100 g a.i./100 kg seed, emergence of other seven fungicides seed-coating treatments were not significantly different. The incidence of three peanut soilborne fungal diseases seed-coated by all the fungicides significantly decreased. The control efficacies of difenoconazole FS and CS at the rates 100 and 200 g a.i./100 kg seed, fluazinam CS and pyraclostrobin EC at the rate 160 g a.i./100 kg seed, pyraclostrobin CS at the rates 80 and 160 g a.i./100 kg seed, fludioxonil FS at the rate 40 g a.i./100 kg seed and triflumizole FS at the rate 100 g a.i./100 kg seed for peanut crown rot and root rot were higher, with 73.13%-85.15%. The control efficacies of difenoconazole FS and CS at the rate 200 g a.i./100 kg seed, fluazinam CS at the rate 160 g a.i./100 kg seed, pyraclostrobin CS at the rates 80 and 160 g a.i./100 kg seed for sclerotium blight were higher, with 72.77%-84.56%. Seed-coating with all fungicides significantly increased the pod yield. Seed-coating using pyraclostrobin CS at the rates 160 g a.i./100 kg seed, the yield growth rate ranged from 11.77% to 16.50%.