Black Rot (grape) - Environmental Conditions For Infection

Environmental Conditions For Infection

When the weather is moist, ascospores are produced and released throughout the entire spring and summer, providing continuous primary infection. The black rot fungus requires warm weather for optimal growth; cool weather slows its growth. A period of 2 to 3 days of rain, drizzle, or fog is also required for infection." 3 "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.” 4 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. During August, the pycnidia are transformed into an overwintering stage that, in turn, gives rise to pseudothecia within which the spring spores (ascospores) are produced. This (ascospore) is "forcibly discharged into the air and can travel considerable distances."5 "Research has shown that ascospores are an important source of primary infections in the spring."5In the spring during wet weather, the "pycnidia on infected tissues absorb water and conidia are squeezed out."5"Conidia are splashed about randomly by rain and can infect any young tissue in less than 12 hours at temperatures between 60-90 degrees."5A film of water on the vine surface is necessary for the infection to inoculate.5 This completes the disease cycle.” 3