Citrus canker, caused by the bacterium Xanthomonas citri subsp. citri, is an endemic and quarantine disease in northeastern Argentina. Mid-season fruit canker intensity observations (1991-2008) in grapefruit cultivar in Bella Vista (Corrientes), were binary and ordinal categorized. From daily weather elements moisture and temperature variables were calculated in time periods beginning after accumulating 372 degree-days (DD) since 10 July, and fini-shing when the sum reached 985 DD (base Td = 12.5 °C) and from 930 DD to 1175 DD, respectively. The best logistic regression models included the effect of the interaction between DPr (days with precipitation > 12 mm) and DPTxn (days with maximum temperature ≤ 28 °C and minimum ≥ 14 °C ) with prediction accuracies of 94.4 % (binary) and 83.3 % (ordinal). Both logistic models were run in 14 sites of Spain and in Bella Vista, from 1980 to 2008. DPr was the most limiting weather factor for the bacterial expression in the spanish citrus sector, reaching a median value of zero in areas of high production. The temperature factor was clearly favorable for the disease progress. The effect of the interactive component (DPr*DPTxn) reduced dominantly to zero the probability that disease reach moderate to severe levels in Spain, differing with 51.7 % of the years in Bella Vista.

Due to the recent occurrence of citrus canker in the NW region of Argentina there is a lack of information locally generated about the optimum timing of copper sprays for its chemical control. The disease is endemic in the NE of Argentina and successful programs of sprays were generated in that region. The objective of this work was to determine the timing of copper sprays to control canker on leaves of Limoneira 8A lemon in Famaillá, Tucumán. Sprays of copper oxychloride 50 % WP Cupravit® (50 % Cu) were applied at high pressure and high volume until run-off on three leaf-flushes: January 2004, February 2004 and November 2004, and to 0, 14, 21 and 28 days after initiation of shoot development. The incidence of canker (%) on the shoots and leaves was determined 30 days after the last spray application. The best results were obtained when leaf-flushes were sprayed at initiation of shoot development (3.6 cm in length) and until 14 days old (10.6 cm in length). The spray applied in this period achieved the lowest levels of incidence. These results were very similar to those obtained in the NE indicating that the programs developed in that region can be applied to control citrus canker on lemon in Famaillá, Tucumán.