Divisi
Root rot
Fusarium solani · Fungal
Photo: Fred Brooks from United States University of Hawaii at Manoa · CC BY 3.0 us
Root rot is a soil-borne fungal disease of grain legumes such as beans, cowpeas, soybeans, groundnuts and peas. The fungus (a Fusarium-led complex) lives in the soil and attacks the roots and the stem just below and above the ground, rotting away the fine feeding roots and browning the taproot so the plant can no longer draw up water and food. It hits hardest in cold or warm wet ground that drains poorly or is compacted, and it strikes young plants first — from just after they come up through their early growth.
Davide Palmieri1 · CC BY-SA 3.0 
Davide Palmieri1 · CC BY-SA 3.0
Why it matters
Root rot rots the roots your plants feed with, so they starve and wilt even when the soil looks wet. In a bad, wet season it can wipe out up to 7 in every 10 plants (70% of your crop) — whole patches simply fail to grow. It is one of the hardest problems to beat because the fungus lives in the soil for years and does its damage underground where you cannot see it or spray it; once a plant's roots are rotted there is no cure — you can only protect the healthy plants and the next crop.
When to act
patches of yellowing, stunted or wilting seedlings with discoloured roots on sampling
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 root rot field guide
- Identify it
- Scout for it
- Control it
13 field-guide sections in the app
The full guide to root rot — 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 root rot?
What you see first (above ground): patches of plants that are stunted, pale or yellow, and wilting in the heat of the day even though the soil is moist. Whole sections of the row stay small while the rest grow away, and some seedlings simply die and leave gaps in the stand.
When should I take action against root rot?
patches of yellowing, stunted or wilting seedlings with discoloured roots on sampling
How do I control root rot?
Prevent it first — this is your strongest tool (cultural). Root rot is beaten mostly in the soil, before planting: rotate away from legumes for at least 3 to 4 seasons (plant maize, sorghum or another cereal instead) so the fungus starves; fix the drainage — plant on ridges or raised beds so water runs off and roots never sit in wet ground; break up hard, compacted soil and dig in compost or well-rotted manure to build healthy, living soil; and plant a tolerant variety where one is sold locally.
Which crops does root rot affect?
Among the crops covered here: Common bean, Cowpea, Groundnut, Soybean.
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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