This disease usually appears on the upper surfaces of leaves as white-grayish spots with a powdery-like texture, while the underside of leaves often appear brown. The infection can occur on both upper and lower leaf surfaces.
Erysiphe necator is a fungal disease that grows only on grapevine tissue. The disease is host-specific, which means that certain pathogens can only infect plants from the same genus or family. In this case, powdery mildew of grapevines can only infect grapes.
Monitoring: Make it a routine to monitor the field regularly and search plants for the presence of powdery mildew on a weekly basis. It is easier and more cost effective to overcome the infestation by controlling it during the initial stage.
It is a common practice to prevent powdery mildew by spraying early in the season on the basis of the growth stage of the vines, namely somewhere around 10-15 centimeters of green vegetative growth.
Consider an application of fungicides every 7-14 days until the grapes have finished changing their color.
Consider an extra application when infected plants have been observed, which is common even under a heavy spraying regime.
Sulfur (dust, wettable, flowable, or micronized) and potassium bicarbonate
Bacillus pumilis and bacillus subtilis