Factors affecting bacterial black spot of mangoes caused by Xanthomonas campestris pv. mangiferaeindicae

Bacterial black spot of mango caused by Xanthomonas campestris by. mangiferaeindicae was found to be essentially a wound pathogen of leaves under glasshouse conditions, with maximum infection occurring at a temperature regime of 22/26 ^oC (night/day). There were significant differences in leaf susceptibility among cultivars, cv. Sensation being less, and cv. Haden more susceptible than cvs Zill and Kent, which agrees with field observations of fruit infection. The organism is a phylloplane resident year round in the field and inoculum levels in the tree canopy affect ultimate fruit infection. The major weather factor affecting fruit infection was rainfall which showed a significant correlation (r = 0–77) with levels of infection after allowing for an approximate 2 wk latent period. Other significant correlations were with a wind/rain index (r = 0–73) and a storm index (r = 0–66). The correlation of disease with the duration of free water was non-significant (r = 0–22).