Concepció Moragrega

1. Introduction Bacterial blight of Persian (English) walnut ( Juglans regia L.), caused by Xanthomonas arboricola pv. juglandis (Pierce) Vauterin et al. [ 1 ], is an economically important disease in walnut producing areas worldwide [ 2 , 3 ]. In addition, X. arboricola pv. juglandis has been recently associated with two emerging diseases in walnut: vertical oozing canker [ 4 ] and brown apical necrosis [ 5 ]. Severe yield losses have been reported in Mediterranean walnut orchards due to X.

Xanthomonas arboricola pv. pruni is the causal agent of bacterial spot disease of stone fruits and almond. The bacterium is distributed throughout the major stone-fruit-producing areas of the World and is considered a quarantine organism in the European Union according to the Council Directive 2000/29/EC, and by the European and Mediterranean Plant Protection Organization. The effect of leaf wetness duration and temperature on infection of Prunus by X. arboricola pv.

A two-step modeling approach was used for predicting the effect of temperature on the growth of Xanthomonas arboricola pv. pruni, causal agent of bacterial spot disease of stone fruit. The in vitro growth of seven strains was monitored at temperatures from 5 to 35°C with a Bioscreen C system, and a calibrating equation was generated for converting optical densities to viable counts.