Divisi
Citrus black spot
Phyllosticta citricarpa · Fungal
Photo: USDA APHIS · Public domain
Citrus black spot is a fungal disease of citrus (oranges, lemons, limes) caused by Phyllosticta citricarpa. Its spores blow and splash off the carpet of old, rotting leaves under the trees during warm, wet summers and infect the young fruit soon after fruit set. The fruit then looks perfectly clean for months, and the ugly spots only appear as it ripens. It scars the rind rather than rotting the flesh, so the fruit stays safe to eat, but the blemish is enough to get a load downgraded, refused by fresh and export buyers, and in bad cases the fruit drops before you can pick it.
Cesar Calderon · CC BY-SA 3.0 
USDAgov · Public domain
Why it matters
Black spot doesn't rot your fruit — it scars the skin with ugly spots, and that alone is enough to get a whole load rejected by fresh and export buyers or dropped to cheap juice-price. A bad year can cost you up to 40% of your crop in downgrades and, on hard-hit trees, in fruit that drops before harvest. It is hard to beat because the fungus infects the young fruit in early summer but the spots stay hidden for months — by the time you see them, the damage to that fruit is already done and no spray can undo it. And the spore factory is the carpet of old fallen leaves under your trees, which re-infects the crop every warm, wet summer unless you deal with it.
When to act
In summer-rainfall citrus areas with the disease present, protect fruit preventively through the susceptible period after fruit set; symptomatic fruit at scouting confirms the need to maintain the spray programme.
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 citrus black spot field guide
- Identify it
- Scout for it
- Control it
12 field-guide sections in the app
The full guide to citrus 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 citrus black spot?
The classic sign — 'hard spot': on ripening fruit, look for small round craters about the size of a match-head to a pea (3–10 mm), each with a sunken grey-to-tan centre, a dark, slightly raised ring around the rim, and a cluster of tiny black dots (pinpricks) in the middle. Those black dots are the fungus's spore factories. Spots show up first and worst on the sun-facing side of the fruit.
When should I take action against citrus black spot?
In summer-rainfall citrus areas with the disease present, protect fruit preventively through the susceptible period after fruit set; symptomatic fruit at scouting confirms the need to maintain the spray programme.
How do I control citrus black spot?
Prevent it first — starve the spore source (the leaf litter). The fungus makes most of its spores in the old leaves rotting under your trees, so the single most useful job costs almost nothing: rake up and remove or compost the fallen leaves, or speed their rotting by mulching over them, spraying them with a little urea, and keeping a ground cover so they break down fast. Do this in the dry months before the summer rains set the spores flying. This sanitation is the strongest non-chemical tool you have.
Which crops does citrus black spot affect?
Among the crops covered here: Lemon, Lime.
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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