Control of bacterial black spot in mango.
Boshoff M., Kotze J. M., Korsten L.
Author Affiliation: Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria, 0001, South Africa.
Yearbook - South African Mango Growers' Association 18 : 36-39
Abstract : Enhanced copper spray programmes and new products were evaluated for control of bacterial black spot of mango, caused by Xanthomonas campestris pv. mangiferaeindicae. Field experiments were conducted during 1997-98 in South Africa on the cultivars Keitt and Kent. In all experiments, both yield and percentage healthy fruit were used as evaluation parameters. Demildex (copper oxychloride) sprayed on it's own at regular intervals (14 days) resulted in the best control. Copper Count N (copper ammonium carbonate) gave poor results when sprayed at 300 ml/100 l, but performance improved when it was sprayed at 500 ml/100 l. Plastic coated fruit bags did not reduce the incidence of bacterial black spot in severely affected orchards, and caused damage to the lenticels and fruit epidermis in extreme heat conditions. Biological control with spray applications of the bacterial antagonist, Bacillus licheniformis, was not achieved. The use of disinfectants, including chlorine dioxide and quaternary ammonium compounds, prior to copper sprays did not reduce the incidence of bacterial black spot in severely affected orchards. Calcium hypochloride sprayed prior to copper significantly controlled bacterial black spot, but a reduction in yield was observed. Similarly, decreased yield was observed with a QAC and chlorine dioxide. A new product (Bion, which systematically activates resistance responses in plants) was evaluated and found to be effective in controlling bacterial black spot. Other products evaluated included an antibiotic (Streptomycin-sulfate) with good control, and Urea, with no control achieved. The results indicate the importance of integrating preventative and curative measures for adequate control.