Two isolated field experiments were carried out to evaluate the effect of copper and copper+carbamate formulations on resident Xanthomonas campestris pv. vesicatoria populations on sweet pepper leaf surfaces, as well as on symptom severity of bacterial spot. In one of the fields, plants of cv. Cascadura Itaipu were inoculated with isolate ENA-818 showing copper sensibility; in the second field the same cultivar was inoculated with isolate ENA-4369 resistant or tolerant up to 900 µg/ml of Cu++ in vitro. In both areas the crops were weekly sprayed with different chemical compounds (copper sulphate, copper oxichloride, cuprous oxide and cuprous oxide+mancozeb) including a control treatment sprayed with distilled/deinonized water. Evaluations carried out during the crop cycle showed that only cuprous oxide and its mixture with mancozeb were able to reduce bacterial population levels. However all chemical treatments differed from the control treatment as related to reduction of functional leaf area estimated by the "Area Under Disease Progress Curve" in the field inoculated with ENA-818. On the other hand, in the field inoculated with ENA-4369 (resistant to copper) the chemical treatments did not differ from the control, indicating that Cu++ concentrations of the products were not sufficient to promote a satisfactory reduction of bacterial spot severity and epiphytic X. c. pv. vesicatoria population after disease onset.
epidemiology; bacterial spot; Capsicum annuum; copper resistance
