Pendugaan penurunan hasil jagung oleh penyakit bulai (Peronosclerospora maydis (Rac) Shaw).
1988
Sudjono M.S. | Sopandi Y.
A simulation study on the yield losses assessment of corn caused by downy mildew disease (Peronosclerospora maydis (Rac) Shaw) had been conducted at Cikeumeuh experimental farm (Bogor) in wet season 1985/86. Seeds of susceptible Metro variety were treated with Ridomil 35 SD. a systemic fungicide contains metalaxyl active ingredient, for disease intensities control. The seed treatments were at the dosage rates of 0.0, 0.5, 0.10, 0.15, and 0.20 grams formulation per kg of seeds. Regression analysis between the fungicide application and downy mildew intensities indicated an exponential function with the coefficient correlation highly significant (r=0.91). From the regression equation can be calculated that the control of downy mildew will be effective at the rate of 2 g/kg of seed in which downy mildew infestation was 60 percent. Disease intensities increased by time from 2 to 8 weeks after sowing, but disease intensity was significantly different between the treated and untreated one. The disease appeared earlier at a rate below 0,10g/kg of seed as compared to the higher dosage ones. Regression analysis between yield losses and disease intensities indicated a negative linear equation with highly significant coefficient correlation (r=-0.98). Maximum yield of Metro variety can be achieved at 1.445 t/ha based on the equation when there is full control of downy mildew disease.
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