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Sweet potato feathery mottle virus with sweet potato chlorotic stunt virus ICTV species: Potyvirus batataplumei (SPFMV) with Crinivirus ipomeae (SPCSV) · formerly or also: SPFMV + SPCSV
Sweet potato virus disease is the most damaging disease of sweet potato. It develops when a plant is infected by two viruses together: sweet potato feathery mottle virus, carried by aphids, and sweet potato chlorotic stunt virus, carried by whiteflies. Alone, each causes little harm; together, plants become severely stunted with small, distorted, pale leaves and give few or no storage roots. Because farmers replant vine cuttings, the viruses accumulate season after season unless clean planting material is used. Farmers who buy or exchange vines from unknown sources often bring the disease into new fields without realising it.
Sweet potato virus disease is caused by Sweet potato feathery mottle virus with sweet potato chlorotic stunt virus, a virus disease caused by two viruses together (synergism), spread by aphids, whiteflies and cuttings (order Patatavirales (SPFMV); Martellivirales (SPCSV), family Potyviridae (SPFMV); Closteroviridae (SPCSV)).
Older or alternative scientific names: SPFMV + SPCSV.
Both viruses occur in most sweet potato-growing regions. The combined disease is most important in East Africa, where it is the main constraint on the crop, and is also reported in West and southern Africa, Asia and the Americas.
| Region | Status |
|---|---|
| East Africa | Widespread; the main sweet potato disease |
| West and southern Africa | Present |
| Asia | Viruses widespread; disease present |
| Americas and Oceania | Viruses present; combined disease reported |
SPFMV is a potyvirus transmitted non-persistently by aphids (Myzus persicae, Aphis gossypii and others); SPCSV is a crinivirus transmitted semi-persistently by the whitefly Bemisia tabaci. SPCSV suppresses the plant's defences, allowing SPFMV to multiply hundreds of times more. Laboratory tests (serology or PCR) identify the viruses.
| Crop stage | What you see |
|---|---|
| Early growth | Stunted plants with small, narrow, distorted leaves, vein clearing and mosaic or chlorosis. |
| Vine growth | Severe stunting, puckered and strap-like leaves, purpling or yellowing; plants stand out in the field as small and pale. |
| Root formation | Few, small or no storage roots; in some varieties cracking of roots. |
Both viruses are carried from season to season in vine cuttings taken from infected plants, and spread within fields by aphids (SPFMV) and whiteflies (SPCSV). Once both are in the same plant, the disease develops within weeks. Plants infected with only one virus may show no clear symptoms, so they are often kept and used as a source of cuttings, carrying both viruses into the next crop.
| Stage | Duration | Notes |
|---|---|---|
| Infected cuttings planted | At planting | Main carry-over route. |
| Vector transmission | Seconds (aphids, SPFMV) to hours (whiteflies, SPCSV) | Field spread. |
| Co-infection and synergism | About 2-4 weeks to severe symptoms | SPCSV boosts SPFMV. |
| Yield loss | Through the season | Few storage roots form. |
Spread follows aphid and whitefly activity, which is greatest in warm weather; symptoms can be milder at high temperatures.
Continuous where sweet potato is grown and replanted year-round.
Repeated use of vine cuttings from the farmer's own or neighbours' fields, overlapping and continuous plantings, high aphid and whitefly numbers, and susceptible varieties.
There is no economic threshold; management is preventive through clean planting material, roguing and resistant varieties.
Yield losses of 50-98% are reported in infected plants of susceptible varieties; field losses depend on how much of the planting material was already infected. Repeated replanting from infected vines leads to a gradual 'degeneration' of a farmer's planting material, with yields falling each season until clean material is introduced.
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 viruses, and insecticides cannot prevent non-persistent aphid transmission. What is registered differs by country and changes over time; follow the label and your local plant-protection authority.
Sweet potato and wild Ipomoea species; the viruses have narrow host ranges centred on the morning glory family.
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.