Analyzing the monocyclic process in sheath blight of rice under semi-controlled conditions
1993
Leano, R.M. | Lapis, D.B. | Savary, S.
Trap rice plants, used as probes, were exposed in quadrats that were inoculated with sheath blight (Rhizoctonia solani Kuhn) to study the spread of the disease. The effects of leaf wetness regime, leaf contact frequency, and strength of inoculum source were quantified using this approach. Environmental variables were manipulated in the quadrats by covering them with plastic cages for different durations (leaf wetness), planting the hills at different spacings (leaf contacts), and varying the amount and placement of inoculum in the canopy (source strength). Each experiment involved three successive batches of trap plants. The infection efficiency increased with the accumulation of wet and dry daily cycles. Incidence and severity on sheaths were increased with increased crop density. Increasing the amount of initial inoculum led to increase of disease incidence, leaf severity, and number of infection points. Most disease variables were higher in treatments involving placement of the same amount of inoculum at the base of the plants. Disease spread declined with the successive batches of trap plants suggesting a decline of the number of infectious lesions over time
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