Divisi
Bacterial black spot
Xanthomonas citri pv. mangiferaeindicae · Bacterial
Photo: Plant pests and diseases · CC0
Bacterial black spot (also called bacterial canker of mango) is a disease of mango caused by a bacterium that survives the dry season inside cracked cankers on the twigs and is splashed onto new leaves, shoots and fruit by wind-driven rain. It slips in through the leaf's natural pores and through tiny wounds made by blowing sand, wind and hail, then shows as angular black spots on the leaves and raised, star-shaped, gum-oozing cracks on the fruit. It thrives in warm (20-30 degrees C), very humid, windy orchards and is worst where blowing sand scratches the leaves and fruit.
Scot Nelson · CC0 
Scot Nelson · CC0
Why it matters
Bacterial black spot attacks the part you actually sell - the fruit. In a warm, wet, windy orchard it can scar, crack and rot up to 6 in every 10 mangoes (60%), turning fruit you would sell at market into fruit no buyer will touch, while its leaf and twig damage slowly weakens the whole tree. It is hard to beat once it takes hold, because the bacteria hide and survive the dry season inside cracks in the twigs, ready to be splashed onto fresh growth by the next windy rain - and copper spray can only protect healthy tissue, it cannot cure a spot that has already formed. That is why beating it is about prevention, cutting out the source, and timing - there is no spray that heals it.
When to act
Begin copper protection at the start of the rains and at flowering and fruit set when black angular spots appear on leaves or young fruit.
This guidance is general, compiled from published agronomic references including FAO and CABI. Thresholds and timing shift with your crop, your variety and the season.
In much of the region a spray is simply called mushonga — medicine. But a chemical group you cannot name is one you cannot rotate, and a product you did not write down has no pre-harvest interval you can observe. Mushonga, and other farming words →
The full bacterial black spot field guide
- Identify it
- Scout for it
- Control it
13 field-guide sections in the app
The full guide to bacterial black spot — every symptom to check, how and when to walk your field looking for it, and the controls that actually work, ranked. Built into your crop plan, so you are told to look before it costs you a harvest.
Crops it affects
Frequently asked questions
How do I identify bacterial black spot?
On the leaves (the first sign): small dark, water-soaked, greasy-looking spots on the young leaves that harden into raised BLACK spots with straight sides - angular, like little tiles - because the veins box them in. Each spot is often ringed by a yellow halo, and you may see black streaks running along the midrib.
When should I take action against bacterial black spot?
Begin copper protection at the start of the rains and at flowering and fruit set when black angular spots appear on leaves or young fruit.
How do I control bacterial black spot?
Prevent - plant it out of trouble: in windy, wet areas choose less-susceptible mango varieties (ask your nursery or extension officer which local varieties are least affected), and start only with clean, spot-free nursery seedlings. Never carry the disease into a healthy orchard on new planting material.
Which crops does bacterial black spot affect?
Among the crops covered here: Mango.
Catch it before it costs you a harvest
Divisi builds scouting into your crop plan — it tells you when to walk your field, what to look for at that stage, and what to do when you find it. Free for farmers, works offline.
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