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Cassava mosaic begomoviruses (African cassava mosaic virus and relatives) ICTV species include Begomovirus manihotis (African cassava mosaic virus); East African and Sri Lankan cassava mosaic viruses are related species · formerly or also: ACMV, EACMV, SLCMV
Cassava mosaic disease is the most important disease of cassava, a staple for hundreds of millions of people in Africa and a major crop in Asia. Several related viruses cause yellow-green mosaic and distorted, shrunken leaves, and badly affected plants produce few or no usable roots. It spreads mainly through infected stem cuttings used for planting and by whiteflies. Resistant varieties and clean planting material control it well.
Cassava mosaic disease is caused by Cassava mosaic begomoviruses (African cassava mosaic virus and relatives), a virus complex (begomoviruses with single-stranded DNA genomes), spread by whiteflies and infected cuttings (order Geplafuvirales, family Geminiviridae).
Older or alternative scientific names: ACMV, EACMV, SLCMV.
Present across virtually all of sub-Saharan Africa and in Indian Ocean islands, and in South Asia (India and Sri Lanka). A severe recombinant strain caused a pandemic that spread from Uganda across East and Central Africa from the late 1980s. Sri Lankan cassava mosaic virus was found in Cambodia in 2015 and has spread in mainland Southeast Asia. Cassava in the Americas is not affected by these viruses.
| Region | Status |
|---|---|
| Sub-Saharan Africa | Widespread; severe pandemic strains in East and Central Africa |
| South Asia | Indian and Sri Lankan cassava mosaic viruses widespread |
| Southeast Asia | Sri Lankan cassava mosaic virus spreading since 2015 |
| Americas | Absent; quarantine concern |
Several virus species and many strains, often occurring as mixed infections that cause more severe disease; laboratory tests (PCR) identify them. Transmission is by infected cuttings and by the whitefly Bemisia tabaci in a persistent, circulative manner.
| Crop stage | What you see |
|---|---|
| Sprouting (from infected cuttings) | The first leaves are already mottled and distorted; such plants are the main source of spread. |
| Vegetative growth | Yellow or pale green mosaic patches on leaves, leaf distortion and curling, narrow and reduced leaflets; severe cases have tiny, misshapen leaves and stunted plants. |
| Root development | Fewer and smaller storage roots; severely affected plants produce almost no harvest. |
Most new infections in a field come from planting cuttings taken from infected plants. Whiteflies then carry the virus from infected to healthy plants, mostly to young plants in the first few months. Recovery of symptoms in some resistant varieties is common, but infected plants keep the virus in their stems, so cuttings from them carry it to the next crop.
| Stage | Duration | Notes |
|---|---|---|
| Infected cuttings planted | At planting | Main source of disease. |
| Whitefly acquisition and transmission | Hours of feeding; whitefly remains infective for days | Spread highest when whitefly numbers are high. |
| Symptom development | About 3-5 weeks after whitefly infection | Young plants most affected. |
| Carry-over in stems | To the next crop | Through cuttings. |
Spread follows whitefly abundance, which is greatest in warm, moderately humid lowland seasons.
Continuous spread where cassava is grown year-round.
Using cuttings from infected fields, high whitefly populations, susceptible local varieties, and continuous cassava cropping with infected volunteers nearby.
There is no numeric economic threshold. Management is preventive: plant symptom-free cuttings of resistant varieties and remove infected plants early.
Yield losses of 20-90% are reported in susceptible varieties depending on virus strain and time of infection, and the disease is estimated to destroy several million tonnes of cassava roots a year in Africa. The East African pandemic in the 1990s caused food shortages in parts of Uganda.
Control works best as a sequence: prevent, monitor, then act only when a threshold or a risk forecast says so, using the least disruptive option that works.
No chemical controls the virus. Insecticides against whiteflies are not practical or economic in most cassava systems. What is registered differs by country and changes over time; follow the label and your local plant-protection authority.
Cassava (Manihot esculenta) and wild Manihot species; a few other plants have been infected experimentally or occasionally in the field.
How to grow the crop well is the first line of defence. Laisha's free grow guides cover each crop from sowing to harvest:
Written by Laisha from the sources above, in its own words. This page is general reference, not a prescription: confirm identification locally and follow the label and your plant-protection authority.