The three combining factors that result in disease in a vineyard are:
1) A susceptible plant
2) The presence of a pathogen, and
3) Environmental conditions that either favor the pathogen’s
spread or reduce the plant’s ability to ward off diseases.
The latter, favorable environmental conditions, is the primary factor that can influence key management decisions, including when, what, and how frequently to spray or implement other disease control tactics. In this fact sheet, we describe key windows of vine development, and key environmental conditions, that drive the severity of grape powdery mildew, grape downy mildew, Botrytis bunch rot, Phomopsis cane and leaf spot, black rot, and anthracnose diseases. This will highlight why some years are “tough” for the management of certain diseases, and why environmental conditions are critical to consider when developing disease management program.