Bacterial black spot of mangoes.
Pitkethley R.
Author Affiliation: Diagnostic Services, Darwin, Australia.
Agnote - Northern Territory of Australia : 2 pp.
Abstract : Bacterial black spot was first recorded in the Northern Territory, Australia, in 1981 in the Darwin area. Since then it has appeared in most areas in the Top End where mangoes are grown. The bacterium that causes black spot is called Xanthomonas campestris pv. mangiferaeindicae. It can attack leaves, twigs and fruit. The symptoms include: black and raised leaf spots with angular shape; black and cracked twig and stem lesions; and black scabby spots (with water-soaked margins) are formed on the fruit, often with star-shaped cracks within them. The bacteria are harboured in stem lesions on seedlings and on bud wood, which act as reservoirs from which the disease can spread to leaves and fruit. The bacteria may be present without visible symptoms and may not be detected until the mango plant has grown. The disease can spread from tree to tree in the field by wind-driven rain or through implements used for management activities such as pruning. Infection is favoured by warm humid conditions with intermittent rain. Several copper spray formulations are registered in the Northern Territory and recommended for the control of mango bacterial black spot. Chemical control should be used in conjunction with the following management practices that will help to keep the pathogen away, prevent its dispersal or minimize the initiation of infection: use disease-free planting stock; prune to remove infected branches (sources of inoculum) and to improve aeration within the tree; practice hygiene such as sterilization of pruning and harvesting implements; provide windbreaks to minimize wind damage (creation of infection sites) and the spread of the bacterium by wind; use resistant cultivars where possible. Unfortunately, cv. Kensington Pride, the highest demand in the market, is relatively susceptible.