ABSTRACT

Studies on major fungal diseases of rice (Oryza sativa L.) were carried out in the Laboratory, greenhouse and experimental field at Umudike Umuahia, Abia State and farmers rice field at Izzi local Government Area of Ebony state. Disease survey was carried out in major rice growing areas in selected four Local Government Areas in each State of the southeastern Nigeria in 2009 and 2010 seasons showed percentase diseases incidence and severity up to 98.60% and 3.20 respectively. Eleven fungal isolates viz: Aspergillus niger, Botridiploidia oryzae, Curvalaria oryzae, Fusarium moniliforme, Fusarium oxsporium, Fusarium solani, Helminthosporium oryzae, Penicillum spp, Phoma oryzae, Trichoconis padwickii and Rhizophus sporangia. The seed health test showed that Fusarium moniliforme occurred highest in Abia, Helminthosporium oryzae in Anambra, Trichoconis padwickii in Ebonyi, Phoma oryzae in Enugu while Fusariim oxysporum in Imo state. The four fungi organisms proved pathogenic to healthy rice plants during pathogenic test. Germination percentage up to 97% was obtained in Faro 44 while germination failure up to 99% was obtained in BG90 from Imo state. Intercropping rice with soybean increased yield up to 0.56t/ha but had the highest disease incidence of 64.1% and severity of 3.25 in the first year and same in the second year only differed in disease incident and severity ofin which rice + maize mixture had the highest disease incidence and severity of 30.0% and 2.67 respectively. Sowing space of 15cmxl5cm had the highest yield up to 11.26t/ha as well as the highest disease incidence and severity of 69.72 % and 2.88 respectively. Early July had also the highest yield as well as disease incidence and severity of 12.44t/ha, 72.62% incidence and 3.21 severity score. Seedling method produced higher yield (12.05t/ha) than direct seeing which had yield of 10.5t/ha but had the higher disease incidence of 70.83% and severity of 3.21. There was differences in effect of plant extracts with different extraction methods, the crude aqeous extract of Azadiractha indica had the highest mycelial growth inhibition up to 52% at extract concentration of between 10%-30% in F.moniliforme while Garcinia cola in ethanol extraction had the best mycelial growth inhibition in Fusarium moniliforme up to 50%. Aqeous extract of Azardiractha indica (neem) had the highest mycelial growth inhibition up to 52.80% in Helminthosporium oryzae while Zingiber officinale (ginger) in ethanol extraction had the best inhibition in the same organism. Also Azadirachta indca by aqeous extraction had the best inhibition up to 60.9% in Phoma oryzae while Piper guinensis (Alligator pepper) by ethanol extraction performed best in growth inhibition up to 69.30% in Phoma oryzae. The synthetic fungicides evaluated inhibited mycelial growth up to 47%. The plant extracts were as effective as the synthetic fungicides in inhibiting mycelial growth. There was a significant difference at 5% probability level for the two plant extracts in reducing disease incidence and severity in rice plants in in- vivo greenhouse experiment where Z. officinale performed better than P.guinensis. In- vivo experiments also revealed that it was better to apply both plant botanic fungicides and synthetic fungicides before infection. The two synthetic fungicides were very effective in.reducing disease incidence and severity in rice plants in the greenhouse but Apron plus performed better than Benlat