ABSTRACT: Air-dried aqueous leaf extracts of Carica papaya, Chromolaena odorata and Azadirachta indica were screened for antifungal properties against Sclerotium rolfsii, causing cormel rot disease in cocoyam at 50, 70, and 100% concentrations and Trichoderma koningii (4.9x106spores/ml) in vivo. Dithane M45 (mancozeb) at 2% concentration was also used as positive control for better comparison. The aqueous extracts and T. koningii were applied as preventive and curative control measures against Sclerotium rolfsii. Spraying fresh and healthy cormels inoculated with Sclerotium rolfsii at 3.75x105spores/ml indicates that the plant extracts, Mancozeb and T. koningii had significant preventive and curative effects on disease severity and percentage weight loss on diseased cocoyam cormels. Preventive and curative application of T. koningii significantly reduced disease severity, though the later was not significantly different from the other control methods. Specifically, highest disease severity was observed in C. papaya at 50% concentration. The plant extracts and dithane M45 (fungicide) were more effective as curative, while T. koningii was more effective in the preventive method. On percentage weight loss, C. odorata at 70% concentration gave the highest (49.61%), followed by C. papaya (50%) with 47.85% and the least (23.77%) was observed in A. indica at 70% concentration. Therefore, the curative method revealed the effects of the different management methods on the percentage weight of cormels affected by rot. However, C. odorata and A. indica 50 at 100% concentration respectively, significantly reduced weight loss in cormels, while C. odorata (100% concentration) and the control gave the highest percentage weight loss in the curative treatment. From these findings, we conclude that the plant extracts and T. koningii were more effective in controlling cocoyam cormel rot and reduce weight loss than the synthetic fungicide Mancozeb.
Key words: Sclerotium rolfsii, Colocasia esculenta, Plant extracts, Curative and preventive control.
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