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Volume: 5, Issue: 6, Nov-Dec, 2017
Preventive and curative control of sclerotium rot disease of cocoyam cormel (Colocasia esculenta [L., Scott]) using plant extracts and Trichoderma koningii
Nwauzoma Akagbuo Bartholomew, Jaja Tamunodiari Emylia, Njoku Chibuzor
Aqueous leaf extracts from air-dried samples of Carica papaya, Chromolaena odorata, and Azadirachta indica were screened for antifungal properties against Sclerotium rolfsii at 50, 70, and 100% concentrations and Trichoderma koningii (4.9 × 106 spores/ml) in vivo. Dithane M45 at 2% concentration was used as positive control for better comparison. The aqueous extracts and T. koningii were applied as preventive and curative methods by spraying fresh and healthy cormels with S. rolfsii (3.75 × 105 spores/ml). The results showed that Mancozeb and T. koningii had significant effect (preventive and curative) on disease severity and percentage weight loss. Furthermore, preventive and curative application of T. koningii significantly reduced disease severity. C. papaya at 50% concentration (preventive method) had the highest disease severity (3.8%), as to the control (4.0%). The extracts and dithane M45 were more effective as curative, while T. koningii was better as preventive method. The result on percentage weight loss showed that C. odorata (70% concentration) had the highest (49.61%), followed by C. papaya (50%) with 47.85%, and the least was A. indica (23.77%) at 70%. C. odorata and A. indica 50% and 100% concentrations, respectively, significantly reduced weight loss, while C. odorata (100% concentration) and the control gave the highest percentage weight loss in the curative method. Conclusively, plant extracts and T. koningii were more effective in controlling the disease and reduction in weight loss than mancozeb.
Keywords: Sclerotium rolfsii, Colocasia esculenta, Plant extracts, Curative, Preventive control.