Model for forecasting the leaf spot disease in apple trees based on temperature and leaf wetness duration

Abstract

The effect of temperature and leaf wetness duration on the development of Glomerella leaf spot disease was characterized in greenhouse study. Potted apple plants of cv. Gala were inoculated with C. gloeosporioides (106 conidia/ ml), and submitted to 12, 14, 16, 18, 20, 22, 24 and 26°C under continuous wetness (8, 10, 12, 18, 24, 30, 36, 42, 48, 54, 60,
66, 72 and 96h). The best equation to explain the interaction between leaf wetness duration (LWD, h) and temperature (T,ºC) on the severity of Glomerella leaf spot was Y = -91,497 + (7,851 x T) + (0,243 x LWD) + (-0,177 x T x T) + (0,021 x T x LWD) + (-0,002 x LWD x LWD).