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Bean Common Mosaic Virus DiseaseIdentification & Treatment Guide 2026

Bean common mosaic virus (BCMV) · Family: Potyviridae

Bean common mosaic virus (BCMV) causes green mosaic mottling, leaf curling, and stunting in common bean. Seed transmission (5-35%) perpetuates the virus. Manage with resistant varieties carrying bc genes, certified virus-free seed, aphid management, and roguing infected plants. Avoid varieties with only the I gene in areas with Bean common mosaic necrosis virus (BCMNV).

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Quick Diagnosis

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Bean Common Mosaic Virus Disease

Affects: leavespodsseeds
Peak Season: Throughout the growing season; aphid-mediated spread peaks during dry spells within the rainy season
Spread Risk: Fast
Spread By: Seed-borne (5-35%), aphid vectors (non-persistent, 20+ species), mechanical transmission

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Symptoms: What does Bean Common Mosaic Virus Disease look like?

Visual identification guide — tap each stage for details

Light-dark green mosaic mottling on bean trifoliate leaf from BCMV — Characteristic light/dark green mosaic on trifoliate leaf

Downward leaf curling and blistering on bean from BCMV — Leaf curling, blistering, and narrowing from BCMV

Systemic necrosis black root killing bean plant with I gene — Lethal systemic necrosis (black root) in I-gene variety

Early Stage

Light-dark green mosaic on young leaves
Alternating light green and dark green areas (mosaic) appear on trifoliate leaves. Leaves may be slightly puckered or cupped.

Mid Stage

Leaf curling, blistering, and stunting
Leaves develop pronounced downward curling, blistering (rugosity), and narrowing. Plants become stunted with shortened internodes. Pods may be curved and reduced in size.

Late Stage

Severe yield reduction or systemic necrosis
Yield losses of 25-98% depending on variety and infection timing. In varieties carrying the I gene exposed to BCMNV, lethal systemic necrosis (black root) kills plants rapidly — stems, petioles, and roots turn black.

Causes: Why is my plant getting Bean Common Mosaic Virus Disease?

Environmental triggers and disease cycle

Planting BCMV-infected seed — the primary perpetuation mechanism
Aphid transmission from infected to healthy plants
Informal seed systems lacking virus testing
Proximity to infected bean fields

Disease Lifecycle

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Host Plant

Susceptible crop

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Pathogen

Potyvirus

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Conditions

Throughout the growing season; aphid-mediated spread peaks during dry spells within the rainy season

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Infection

Penetrates tissue

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Symptoms

Visible signs

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Spread

Seed-borne (5-35%)

Often confused with: Bean Angular Leaf Spot, Soybean Mosaic Virus Disease, Cowpea Mosaic Virus Disease. See our comparison guide.

How to Treat Bean Common Mosaic Virus Disease

Tick each step as you complete it — works offline too

🌿 OrganicSafe for all farms

Organic Treatment Steps

4 steps

Plant certified virus-free seed from tested, accredited seed sources.
Use varieties with recessive resistance genes (bc-1², bc-2², bc-3) for durable protection.
Rogue symptomatic plants within 30 days of emergence — before aphids spread virus widely.
Do NOT save seed from BCMV-infected fields for replanting.

🧪 ChemicalUse protective equipment

Chemical Treatment Steps

3 steps

Insecticides are ineffective against non-persistently transmitted viruses like BCMV — aphids transmit before being killed.
Mineral oil sprays (paraffinic oil 1%) may reduce aphid transmission marginally in seed production fields.
Focus efforts on clean seed and resistant varieties rather than chemical approaches.

Prevention & Seasonal Calendar

Year-round protection plan for your crops

Pre-Planting

Plant certified virus-free seed — the single most important prevention
Use BCMV-resistant varieties with bc gene combinations

Mid-Season

Avoid the I gene alone in areas where BCMNV is present (East Africa)
Rogue infected plants early in the season

Post-Harvest

Isolate seed multiplication fields from commercial bean fields
Never save seed from visibly infected plants or fields

🛡️ Resistant Varieties

Varieties with bc-3 gene (broadest resistance)CELRK (bc-1² + bc-2²)Rojo de Seda (I + bc-3)

🌼 Companion Planting

These plants can reduce Bean Common Mosaic Virus Disease pressure when grown nearby:

maize

View full seasonal calendar for your region →

Frequently Asked Questions

Common questions about Bean Common Mosaic Virus Disease

What is 'black root' and why does it happen?

Black root (systemic necrosis) occurs when a bean variety carrying the dominant I resistance gene is infected with temperature-insensitive strains of BCMV or with Bean common mosaic necrosis virus (BCMNV). Instead of preventing infection, the I gene triggers a hypersensitive response throughout the plant, killing it. This is why breeders in East Africa (where BCMNV is common) avoid using the I gene alone and prefer recessive bc genes.

How does seed transmission perpetuate BCMV?

BCMV infects the embryo of developing seeds. When infected seed is planted, 5-35% of seedlings emerge already infected. These serve as virus sources for aphid transmission to neighboring healthy plants. In informal seed systems where farmers save and share seed without virus testing, BCMV accumulates in seed lots over generations, reaching very high infection rates.

Can virus-free seed eliminate BCMV from a region?

Using virus-free seed can dramatically reduce but not completely eliminate BCMV because aphids can introduce the virus from distant infected fields or wild legume hosts. However, starting with clean seed reduces initial inoculum so dramatically that epidemic development is delayed and yield losses are minimized. Clean seed + resistant varieties is the gold standard.

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Related Disease

Bean Angular Leaf Spot

Pseudocercospora griseola

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Related Disease

Soybean Mosaic Virus Disease

Soybean mosaic virus (SMV)

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Affected Plant

Common Bean

Phaseolus vulgaris

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Treatment Guide

Full Treatment Protocol

Detailed spray schedule & dosage guide

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