Divisi
Tobacco brown spot
Alternaria alternata · Fungal
Photo: R.J. Reynolds Tobacco Company Slide Set, R.J. Reynolds Tobacco Company, Bugwood.org · CC BY 3.0 us
Tobacco brown spot is a leaf-spot fungus (Alternaria alternata) that feeds mainly on old, ripening and over-ripe tobacco leaves. It is a weak fungus — it rarely troubles young, healthy, fast-growing leaf, but once the bottom leaves start to age, ripen or get damaged it moves in, especially in warm, humid weather with heavy dew. It makes the tell-tale target-ring spots on the lower leaves — the very leaves that are your first harvest — and it keeps working on picked leaf in the curing barn, so the loss can follow the crop indoors.
Why it matters
Tobacco brown spot hits you where it hurts most — the lower leaves that ripen first and are your earliest harvest. In a bad year, on an over-ripe, humid crop, it can rot and downgrade up to 3 in every 10 leaves (30% of your crop), and even light spotting drops a leaf into a cheaper grade so buyers pay you less. The worst of it is that it does not stop at harvest: the fungus keeps eating picked leaf in the curing barn if the leaf goes in damp or spotted, so a leaf that looked saved can still be lost. Because it feeds on ageing leaf, the clock is your enemy — leaf left too long on the plant is exactly what it wants.
When to act
first target-ring spots found on the ripening lower leaves — pick those leaves promptly; if spots appear on the lower leaves of about 1 in 10 plants (10%) while warm, humid weather holds and the leaf is not yet ready to pick, start protectant sprays
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 tobacco brown spot field guide
- Identify it
- Scout for it
- Control it
15 field-guide sections in the app
The full guide to tobacco brown 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 tobacco brown spot?
The first thing you see: round brown spots on the older, lower leaves, usually 1 to 3 cm across (about the size of a fingernail to a large coin). Look closely and each spot has rings inside it, one inside the other, like a target or an archery board (this is 'target spot'), and each spot is ringed by a yellow halo where the green fades. It always starts low down, on the oldest, most ripe leaves first — not on the young top leaves.
When should I take action against tobacco brown spot?
first target-ring spots found on the ripening lower leaves — pick those leaves promptly; if spots appear on the lower leaves of about 1 in 10 plants (10%) while warm, humid weather holds and the leaf is not yet ready to pick, start protectant sprays
How do I control tobacco brown spot?
Prevent it first — pick ripe leaf on time (your strongest tool, no sprayer needed): brown spot lives on over-ripe, ageing leaf, so prime (pick) the lower leaves as soon as they are ripe and never leave ripe leaf hanging on the plant to over-ripen. Picking on time simply starves the fungus of the old leaf it needs — this one habit prevents most of the damage.
Which crops does tobacco brown spot affect?
Among the crops covered here: Tobacco.
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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