Efficacy of Agry-gent for control of bacterial black spot (Xanthomonas campestris pv. mangiferaeindicae) in mango.
Boshoff M.
Author Affiliation: South African Mango Growers' Association, P.O. Box 2321, Tzaneen 0850, South Africa.
: 125-130
Abstract : Current control measures against bacterial black spot (BBS) of mangoes are inadequate and it is generally believed that the extensive spraying of copper is becoming uneconomical. Agry-gent, a commercial plant formulated antibiotic consisting of 100 g gentamycin [gentamicin]/kg and 300 g oxytetracycline/kg, in combination with copper oxychloride spray applications was evaluated as alternative control strategy. In addition, gentamycin applied through micro-injectors was tested for efficacy against BBS. Results of the 1998/99 season indicated significant disease control with Agry-gent (in a copper based spray programme) used at 75, 100 (added penetrant) and 200 g/100 litre. The standard fortnightly application of copper oxychloride proved to be the best treatment in these trials. Two control strategies were evaluated during the 1999/2000 season. A preventative strategy (copper based spray programme and Agry-gent applied early in the season at monthly intervals) resulted in very low levels of disease and the all the Agry-gent treatments had a tendency to outperform a standard copper oxychloride spray programme at fortnightly intervals. A curative strategy (Agry-gent applied with the onset of disease symptoms) overall showed higher disease incidence compared with a preventative strategy. All Agry-gent treatments consequently had a more pronounced effect on the disease and showed a statistically better control when sprayed at 200 g/100 litre (added penetrant). Gentamycin applied through micro-injectors showed no beneficial effect against BBS and phytotoxicity in the form of fruit discoloration was observed.