Ecological factors associated with sheath blight epidemiology and yield loss in rice (Oryza sativa L.)
1993
Leano, R.M.
The infection efficiency in sheath blight significantly increased with prolonged wet and dry daily cycles, particularly with three days of intermittent wet and dry (12/12 h) periods. Incidence and severity on sheaths were increased with increased crop density. Increasing the amount of initial inoculum led to significant increase of disease incidence, leaf severity, and number of infection points. Most disease variables were higher in treatments involving placement of inoculum at the leaf level compared to placement of the same amount of inoculum at the base of the plants. There was a decline of disease variables from batch 1 to batch 3 suggesting a decline of the number of infectious lesions over time. Sheath blight was particularly enhanced in treatments where plants were inoculated at the leaf level. In these treatments, yield loss was especially reflected on the reduced number of filled grains per panicle. There was a significant effect of the development stage of the crop at the time of inoculation on yield loss. Sheath blight intensity and yield loss were higher in plots where flooding was intermittent compared to continously-flooded ones
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