Divisi
Cassava bacterial blight
Xanthomonas axonopodis pv. manihotis · Bacterial
Photo: Raizkgh · CC0
Cassava bacterial blight is a disease of cassava caused by bacteria that live inside the plant's sap tubes. It shows up as angular, water-soaked leaf spots that grow into blight and wilting, amber gum oozing from the stems, and dieback of the growing tips. It spreads fastest in warm, wet, windy weather through rain-splash, shared tools and human movement — but its most dangerous journey is hidden inside infected stem cuttings, which carry it long distances and straight into next season's field.
Why it matters
Cassava bacterial blight can take up to 90% of your harvest in a bad, wet season — that is 9 plants in every 10 worth of roots and leaves lost. It lives inside the plant's sap tubes, so no spray can reach in and cure it. Worst of all, it travels hidden in the stem cuttings you replant — save stems from a sick plant and you carry the disease straight into next year's field. Once it is in your cuttings and your soil, it is very hard to get out, which is why stopping it before it arrives matters far more than fighting it after.
When to act
first angular water-soaked leaf spots or wilting shoots; act on the whole field, not single leaves
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 cassava bacterial blight field guide
- Identify it
- Scout for it
- Control it
14 field-guide sections in the app
The full guide to cassava bacterial blight — 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 cassava bacterial blight?
The first sign — spots that look wet: small angular, water-soaked spots appear between the leaf veins, mostly on the lower and middle leaves. They look dark, greasy and see-through, as if oil or water is trapped in the leaf. Look in the early morning while the dew is still on the plant and hold a leaf up to the light — that is when the wet, greasy patches show up best. Because the veins box them in, the spots have straight, angular edges, not round ones.
When should I take action against cassava bacterial blight?
first angular water-soaked leaf spots or wilting shoots; act on the whole field, not single leaves
How do I control cassava bacterial blight?
Prevent it first — this is where you win or lose: blight rides inside the stem, so your cuttings decide everything. Take cuttings only from strong, healthy plants that showed no spots, gum or dieback last season, and where you can, plant a resistant or tolerant variety — a resistant variety is the single most powerful and longest-lasting protection you have. Never take or plant cuttings from a field that had blight.
Which crops does cassava bacterial blight affect?
Among the crops covered here: Cassava.
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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