Divisi
Bean common mosaic virus
Bean common mosaic virus · Viral
Photo: Howard F. Schwartz, Colorado State University, Bugwood.org · CC BY 3.0
Bean common mosaic virus (BCMV) is a seed-borne potyvirus of common bean. It enters a field hidden inside infected seed — so some seedlings emerge already sick — and is then carried plant-to-plant by aphids in a fast, 'non-persistent' way (an aphid infects a new plant within seconds of probing, which is why sprays cannot stop it). Infected young plants show a light-and-dark green leaf mosaic, down-curled and puckered leaves, and stunting; in susceptible varieties it turns into a lethal black-root necrosis. Early infection can cost most of the crop.
Lololo321 at Portuguese Wikipedia · CC BY 4.0 
Howard F. Schwartz, Colorado State University, Bugwood.org · CC BY 3.0
Why it matters
Bean common mosaic is a virus — a sickness inside the plant's sap, not a bug you can pick off or a spray you can buy — and there is no cure once a plant catches it. Caught while the beans are young, it can cost you up to 80% (four-fifths) of your harvest: the plants stay stunted and give few pods or none. It sneaks in hidden inside infected seed, then aphids carry it from plant to plant in seconds, so you cannot spray it away once it is in the field. That is why clean seed, a resistant variety, and pulling out sick plants early matter more than anything you can do later.
When to act
Rogue mosaic seedlings on sight; manage aphid vectors when colonies build early in the crop.
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 bean common mosaic virus field guide
- Identify it
- Scout for it
- Control it
19 field-guide sections in the app
The full guide to bean common mosaic virus — 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 bean common mosaic virus?
The first and clearest sign — the mosaic: the youngest leaves at the growing tip come up in a patchy mix of light yellow-green and dark green, like camouflage or a mottled shadow, instead of one even green. Healthy new leaves are a smooth, uniform green; sick ones look blotchy. ('Mosaic' just means this light-and-dark patchwork.)
When should I take action against bean common mosaic virus?
Rogue mosaic seedlings on sight; manage aphid vectors when colonies build early in the crop.
How do I control bean common mosaic virus?
Prevent — grow a resistant variety (your single best defence): ask your seed seller for a bean bred to resist bean common mosaic. These carry built-in resistance (breeders call it the I gene or bc genes — you do not need the names, just ask for a resistant or tolerant variety). It is the cheapest and most reliable protection you have.
Which crops does bean common mosaic virus affect?
Among the crops covered here: Common bean.
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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