Influence of Leaf Wetness Duration and Temperature on Infection of Grape Leaves by Elsinoë ampelina under Controlled and Vineyard Conditions

Abstract

On susceptible varieties, indirect damage to vines infected by Elsinoë ampelina range from reduced vigor to complete defoliation while, on berries, damage ranges from reduced quality to complete yield loss. Limited knowledge about the relationship between weather conditions and infection makes anthracnose management difficult and favors routine application of fungicides. The influence of leaf wetness duration and temperature on infection of grape leaves by E. ampelina was studied under both controlled and vineyard conditions. For the controlled conditions experiments, the five youngest leaves of potted vines (Vidal) were inoculated with a conidia suspension and exposed to combinations of six leaf wetness durations (from 0 to 24 h) and six constant temperatures (from 5 to 30°C). A week after each preset infection period, the percent leaf area diseased (PLAD) was assessed. At 5°C, regardless of the leaf wetness duration, no disease developed. At 10 and at 15 to 30°C, the minimum leaf wetness durations were 4 and 6 h, respectively. Above the minimum wetness duration, at temperatures from 10 to 30°C, PLAD increased linearly, with increasing leaf wetness up to 12 h, and then at a lower rate from 12 to 24 h. The optimal temperature for infection was 25°C. Relative infection was modeled as a function of both temperature and wetness duration using a Richards model (R2 = 0.93). The predictive capacity of the model was evaluated with data collected in experimental vineyard plots exposed to natural wetness durations or artificial wetness durations created using sprinklers. In total, 264 vineyard infection events were used to validate the controlled experiments model. There was a linear relationship between the risk of infection estimated with the model and the observed severity of anthracnose (R2 = 90); however, the model underestimated disease severity. A risk chart was constructed using the model corrected for vineyard observations and three levels of risk, with light, moderate, and severe risks corresponding to ≤5, >5% to ≤25, and >25% leaf area diseased, respectively. Overall, 93.9% of 132 independent observations were correctly classified, with 100, 29.4, and 9.4% of the light, moderate, and severe risks, respectively.

Resistance of Vitis germplasm to anthracnose in Southern Brazil

“…reported to be favorable for E. ampelina infection(Santos et al 2020;Carisse et al 2020;Ji et al 2020). In this study, the frequent rainfall and average temperatures, mainly ranging from 15 to 20 o C, created favorable conditions for E. ampelina infection and development.…”

Current status and future prospects of grapevine anthracnose caused by Elsinoe ampelina: An important disease in humid grape‐growing regions

“…The influence of leaf wetness duration, temperature, and age-related susceptibility on infection of E. ampelina was studied to estimate the risk of anthracnose (Carisse et al, 2020(Carisse et al, , 2021. Forecast models are necessary to schedule fungicide application and improve management strategy, but more information is needed to fully understand the epidemiology of grapevine anthracnose.…”

“…First, conidia are formed and released from sclerotia when temperatures reach 2 °C with at least 24 hr of wetness in the spring (Mirica, 1988 ; du Plessis, 1940 ). Second, conidial germination and infection can occur at temperatures ranging from 2 to 32 °C with the optimal temperature between 24 and 26 °C (Carisse et al, 2020 ; Dubos, 2000 ; Li et al, 2018 ; Thind, 1995). On the surface of grape leaves, the conidial germination rate reaches 95% at 26 °C after 24 hr (Malakhova, 1977 ) and 85% at 25 °C after 3 days (Li et al, 2019 ).…”