Quantitative Insights into Grapevine Anthracnose () Epidemiology: Impact of Temperature and Leaf Age on Incubation, Lesion Development, and Sporulation.

Grapevine anthracnose, caused by , is one of the most devastating diseases for wine and table grapes, particularly in hot, humid regions. This study explores how temperature and leaf age affect incubation and how temperature affects lesion development and sporulation. The influence of temperature and leaf age on incubation period (days) was tested under controlled conditions. Leaves from 1 to 8 days old were inoculated and maintained at temperatures of 5, 10, 15, 20, 25, and 30°C. The time elapsed between inoculation and the emergence of initial lesions was recorded. The effect of temperature on lesion development and sporulation was investigated under vineyard conditions. This was achieved through artificial inoculations, with 17, 11, and 11 inoculations conducted in 2016, 2017, and 2018, respectively. The average incubation period, considering all leaf ages, was 27.50 days at 5°C, 15.10 days at 10°C, 9.70 days at 15°C, 5.90 days at 20°C, 3.70 days at 25°C, and 2.26 days at 30°C. Regardless of temperature, the average incubation period was 3.6, 5.9, 8.3, 9.8, 11.9, 13.4, 15.6, and 17.1 days for leaves 1, 2, 3, 4, 5, 6, 7, and 8 days old, respectively. The exponential decay model accurately describes the incubation period as a function of both temperature and leaf age. On average, the relative lesion development (RLD) was 0.00, 0.00, 0.23, 0.47, 0.72, 0.93, 0.92, 0.90, 0.94, and 1.0 at 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 days after inoculation, respectively. The average relative sporulation (RSPO) was 0.03, 0.36, 0.82, 0.96, and 1.0 at 5, 10, 15, 20, and 25 days after inoculation, respectively. Both RLD and RSPO as a function of degree-days (T = 0°C) since inoculation were well described by the logistic function. The rates of change in RLD and RSPO were 0.055 and 0.032, respectively. The results of this study provide new quantitative insights into three important stages (monocyclic processes) in the development of grapevine anthracnose caused by . .