Control of bacterial black spot.
Boshoff M., Kotze J. M., Korsten L.
Author Affiliation: Department of Microbiology and Plant Pathology, Faculty of Biological and Agricultural Sciences, University of Pretoria, Pretoria, 0001, South Africa.
: 51-57
Abstract : During the 1997/98 season in South Africa, enhanced copper spray programmes and new products were evaluated for control of bacterial black spot (Xanthomonas campestris pv. mangiferaeindicae) of mango. Copper oxychloride, Bion [acibenzolar-S-methyl], Copper Count N (500 ml/100 litre) and an antibiotic (Steptomycin-S) were found to be effective in controlling bacterial black spot. During the past season, these products were evaluated in an integrated programme. Timing of applications, dosage and tank mixes with Bion were assessed. In addition, a new antibiotic was evaluated. In all experiments, both yield and percentage healthy fruit were used as evaluation parameters and observations were made once a month throughout the fruit period. Demildex (copper oxychloride) sprayed on its own at regular intervals (14 days) constantly gave the best control. Copper Count N (copper ammonium carbonate) sprays effectively controlled BBS when sprayed at 500 ml/100 litre. The efficacy of Bion was confirmed for the second season and optimum dosage for control was determined. Fortnightly applications from fruit set resulted in effective control. Fruit retention with Bion treatments appeared to be an added advantage. Agrygent, a commercial plant formulated antibiotic consisting of 100 g gentamicin/kg and 300 g oxytetracycline/kg, was sprayed in combination with normal copper oxychloride spray applications to test the efficacy against bacterial black spot of mangoes. Agrygent sprayed at 100 g/100 litre water plus added wetter (Partner) at 100 ml/100 litre showed potential. No differences in yield were found between any of the treatments. The results indicate the importance of integrating preventative and curative measures for adequate control.