Eleven different combinations of Trichoderma harzianum, Psedumonas fluorescens and Validamycin 3L, were applied at different crop stages viz. seed, seedling, tillering and symptoms initiation along with one application of Carbendazim as standard control to test their efficacy against sheath blight of rice caused by Rhizoctonia solani under field condition. One application of Carbendazim @ 0.1% at the time of symptoms initiation (with 81.36 percent reduction of disease incidence, 83.17 percent reduction in disease severity and 62.92 percent inhancement in yield) and seed treatment with Trichoderma harzianum and seedling root dipping with Pseudomonas fluorescens and two spraying of Validamycin i.e. at tillering and symptoms initiation stages (with 69.10 percent reduction of disease incidence,83.17 percent reduction in disease severity and 62.49 percent inhancement in yield) were found to be equally and highly effective in reducing the sheath blight severity and in increasing rice grain yield also. One spraying of Validamycin at symptoms initiation stage was comparatively less effective (29.54 per cent reduction in disease incidence,53.46 per cent reduction in disease severity and 47.76 per cent enhancement in yield ) than one spraying of Carbendazim at symptoms initiation stage.
Abstract:The present paper deals with most susceptible growth stage of rice with different farms and quantitiy of inoculum for development of sheath blight of rice by Rhizoctonia solani.Among seven different growth stages of rice crop i.e. seedling, initial tillering, maximum tillering, boot leaf, panicle emergence, flowering and dough stage, the flowering stage was found to be most susceptible and highly prone for sheath blight development, while seedling stage was found to be least susceptible and with low proneness for disease development. Disease severity, number and length of lesions get increased with the increasing crop growth stages up to flowering stage and thereafter disease severity decreases with the increases in further growth stages of rice plant. Among four different growth stages of the pathogen (inoculum capacity) i.e. five days old mycelium, seven days old mycelium, milky sclerotial stage and mature sclerotial stage which were inoculated at maximum tillering stage of rice plants, five days old mycelial inoculum was found to be most virulent. Disease severity decreased and incubation period increased with further ageing of inoculum. Among five different amount of inoculum (inoculum density) i.e. 0.20 mg, 5.50 mg, 6.00 mg, 7.00 mg and 8.00 mg of sclerotial inoculum, which were inoculated at maximum tillering stage of rice plants, highest disease severity and minimum incubation period was observed with 8.00 mg amount of sclerotial inoculum. Whereas, least disease severity and longest incubation period was observed when inoculation was done with 0.2 mg of sclerotial inoculum.
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