Effect of Environmental Factors on Mycelial Growth and Conidial Germination of Fusicladium eriobotryae, and the Infection of Loquat Leaves.

In Spain, loquat scab, caused by Fusicladium eriobotryae, is usually controlled by fungicides when there are favorable conditions for infection. Lacking specific data on the effect of weather conditions on infection by F. eriobotryae, infection periods are predicted based on the Mills table for apple scab. Experiments were conducted to determine the influence of temperature, wetness duration, relative humidity (RH), and dry periods on mycelial growth, conidial germination, and infection of loquat leaves by F. eriobotryae. F. eriobotryae was able to grow and the conidia to germinate in a wide range of temperatures, whereas no germination occurred at RH < 100%. Maximum conidial germination occurred with 24 h of wetness and germination was strongly reduced by >10 h of dryness interrupting the wetness period. Loquat infection occurred between 10 and 20°C, and disease incidence and severity increased as the duration of wetness period increased. The combined effect of temperature and wetness duration on conidial germination of F. eriobotryae and infection of leaves was described by combining β and Gompertz equations, while the effect of dry periods on reducing the conidial germination was described by a logarithmic equation. The equations developed in this work provided a reasonable fit of the biological processes investigated and could be used for better disease control; they could be further integrated in a disease prediction system for scheduling fungicide sprays against loquat scab.