Divisi
Cassava brown streak disease
Cassava brown streak virus · Viral
Photo: Phillip Abidrabo · CC BY-SA 3.0
Cassava brown streak disease is a viral disease of cassava carried plant-to-plant by tiny whiteflies and spread over long distances inside infected stem cuttings. Its worst damage is hidden — a dry, brown, corky rot inside the storage roots that makes them unfit to eat or sell, often while the plant still looks almost healthy on top. It is one of the most serious threats to cassava in eastern and southern Africa, and because it is a virus there is no spray that can cure it.
Wee Hong · CC BY-SA 4.0
Why it matters
Cassava is often the crop you fall back on when everything else fails — but this disease can rot the roots from the inside and cost you your whole harvest (up to 100%), sometimes while the leaves still look almost healthy. It is a virus, so no medicine or spray can cure a plant once it is infected: a sick plant stays sick and passes the disease to its neighbours through whiteflies and through any cuttings you take from it. Worst of all, the damage hides inside the roots, so you often don't know how bad it is until you dig — and by then it is too late to save that crop. That is why everything depends on starting clean and pulling out sick plants early.
When to act
leaf chlorosis, stem streaks or whitefly build-up; confirm by cutting a few roots to check for necrosis before harvest
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 brown streak disease field guide
- Identify it
- Scout for it
- Control it
16 field-guide sections in the app
The full guide to cassava brown streak disease — 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 brown streak disease?
The first thing you see (leaves): on the middle-aged leaves, a feathery yellow pattern that follows the small side-veins — as if someone painted yellow feathers or blotches along the fine veins while the rest of the leaf stays green. The leaf keeps its normal shape (it is not twisted or crinkled), and it often shows on some leaves or branches and not others.
When should I take action against cassava brown streak disease?
leaf chlorosis, stem streaks or whitefly build-up; confirm by cutting a few roots to check for necrosis before harvest
How do I control cassava brown streak disease?
Prevent — plant a resistant variety (your strongest tool): where one is available for your area, plant a cassava variety bred to resist or tolerate brown streak. Tolerant means it can carry the virus with far less root rot. This single choice protects you more than anything else you can do in the field.
Which crops does cassava brown streak disease 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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