The influence of the temperature (15, 20, 25 and 30ºC) and leaf wetness period (6, 12, 24 and 48 hours) in the severity of the tomato bacterial leaf spot caused by Xanthomonas spp., was studied under conditions climatized chambers. The relative density of lesions was influenced by temperature and leaf wetness duration (P<0,05). Tomato bacterial leaf spot was more severe in the temperature of 25ºC. The data was submitted to non linear regression analysis. The generalized beta function was used for fitting data on disease severity and temperature, while a logistic function was chosen to represent the effect of leaf wetness duration in the severity of the bacterial spot. The response surface resulting of the product of the two functions was express as SE = 0,0001538 * (((x-8)2,4855647 * ((32-x)0,7091962))* (0,64289/(1+21,26122 * exp (- 0,12435*y))), where: SE = represents the estimated severity value (0,1); x, the temperature (ºC) and y, leaf wetness duration (hours). This model will be used as a forecast system for tomato bacterial spot.
epidemiology; plant disease forecaster; Xanthomonas spp.; Lycopersicon esculentum
