Grape black rot originated a raisin in the sun pdf cornell notes eastern North America, but now occurs in portions of Europe, South America, and Asia. It can cause complete crop loss in warm, humid climates, but is virtually unknown in regions with arid summers. The name comes from the black fringe that borders growing brown patches on the leaves.
Grape black rot affects many grape growers throughout the United States, therefore, it is important to understand the disease life cycle and environmental conditions to best manage the disease. Once infection takes place, different methods are available to control the disease. The grape black rot pathogen overwinters in many parts of the grape vine and is able to over winter on the ground . In addition, pathogen can overwinter for at “least 2 years within lesions of infected shoots that are retained as canes or spurs. Some of the mummies on the ground can have a significant discharge of ascospores that begins about 2 to 3 weeks after bud breaks and will mature 1-2weeks after the start of bloom. Infection occurs when either of the spore types land on green grape tissue and tissue remains wet for a “sufficient length of time, which is dependent on temperature.
The period that these overwintering spores are allowed to cause infection depends on the source. If there is a large source for infection, infection will set in early. The infections become visible after 8 to 25 days. When the weather is moist, ascospores will be produced and released throughout the entire spring and summer, providing continuous primary infection. When the weather is moist, ascospores are produced and released throughout the entire spring and summer, providing continuous primary infection.
A period of 2 to 3 days of rain, drizzle, or fog is also required for infection. Conidia spores can also form, within cane lesions or on mummies that have remained within the trellis, and these are dispersed by splashing rain drops. Raindrops transfer these spores by moving the spores to different plant parts, especially susceptible young leaves. If water is present, the conidia germinate in 10 to 15 hours and penetrate young tissue. New black rot infections continue into late spring and summer during prolonged periods of warm, rainy weather. The conidia are capable of germinating and causing infection several months after being formed.
Research has shown that ascospores are an important source of primary infections in the spring. In the spring during wet weather, the “pycnidia on infected tissues absorb water and conidia are squeezed out. Conidia are splashed about randomly by rain and can infect any young tissue in less than 12 hours at temperatures between 60-90 degrees. A film of water on the vine surface is necessary for the infection to inoculate.