Cassava Mosaic Disease: Identification, Control & Resistant Varieties (2026)
クイック回答
Remove and burn all infected plants immediately — this virus has NO cure and spreads rapidly through whiteflies and infected cuttings. Plant only certified virus-free cuttings of resistant varieties (NASE 14, TME 204, NAROCASS 1). Control whiteflies with neem oil (5ml/L) every 7 days. Rogue infected plants within 2 weeks of first symptoms to protect neighboring healthy plants. This disease threatens food security for 500+ million people in sub-Saharan Africa.
どのように見えますか？
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Early infection
Newly emerging leaves show light yellow-green mosaic patterns — irregular patches of normal green and pale yellow/white on the same leaf. The mosaic pattern follows leaf veins. Leaves may be slightly smaller than normal but the plant still looks productive.
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Moderate infection
Mosaic becomes more pronounced with distinct yellow and dark green sectors. Leaves are noticeably reduced in size (50–70% of normal), misshapen, and curled. Some leaves show 'fern-like' distortion. Plant growth is visibly stunted compared to healthy neighbors.
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Severe infection
Leaves are severely distorted — tiny, twisted, and almost entirely yellow-white. Plants are severely stunted (30–50% normal height). Root yield is devastated — tubers are small, woody, and may be absent entirely. In dual ACMV+EACMV infection, the plant may die.
治療方法
Immediately rogue (remove and burn) all infected plants
Uproot the entire plant including roots. Burn on-site or in a designated burn pit — do NOT compost or leave on soil surface. Roguing within the first 2 months after planting is critical to prevent virus spread to the entire field. Mark the spot and replant with clean material.
タイミング: Within 1–2 weeks of first symptom appearance; inspect fields every 7 days
Control whiteflies with neem oil
Mix neem oil (azadirachtin 0.03%) at 5ml per liter of water plus 1ml liquid soap as sticker. Spray on leaf undersides where whiteflies feed and lay eggs. Neem disrupts whitefly feeding, reproduction, and development.
タイミング: Every 7 days during whitefly peak season (transition from dry to wet); every 14 days otherwise
Plant resistant varieties exclusively
NASE 14 (Uganda), TME 204 (West Africa), NAROCASS 1 (Uganda), MM96/5280 (Kenya), TMS 30572 (Nigeria). These varieties carry CMD2 or combined resistance genes. They yield well even under moderate virus pressure.
タイミング: At planting — source cuttings only from certified multiplication sites
Use yellow sticky traps to monitor whitefly populations
Place yellow sticky traps (available commercially or made from yellow-painted boards coated in motor oil) at 10 per hectare, positioned at canopy height. Check weekly — if >20 whiteflies per trap per week, intensify neem spraying.
タイミング: Install at planting; monitor weekly throughout the growing season
最適：小規模農家、有機認証、家庭菜園
Imidacloprid 17.8% SL (for whitefly control only)
Thiamethoxam 25% WG (alternative whitefly control)
IMPORTANT: No chemical cures the virus
最適：大規模農業、深刻な発生
Source only certified virus-free stem cuttings
Get planting material from government-certified multiplication sites, agricultural research stations, or verified community seed systems. NEVER take cuttings from a field with even 1 infected plant — symptomless plants nearby may already be infected but not yet showing symptoms.
Plant resistant varieties — this is the #1 defense
Resistant varieties (NASE 14, TME 204, NAROCASS 1) can tolerate virus infection with minimal yield loss. Even if whiteflies transmit the virus, these varieties recover and produce acceptable yields. This is the most cost-effective strategy for smallholder farmers.
Maintain field hygiene — rogue early and often
Walk through fields every 7 days looking for mosaic symptoms on new leaves. Remove infected plants within 2 weeks of symptom onset. A 3-week delay in roguing increases field infection rates from <5% to >30%.
Avoid planting near old, infected cassava fields
Whiteflies carrying the virus can fly 1–2km. If possible, establish new fields at least 500m from older cassava plots with known infection. Upwind positioning is preferable.
最良の治療は予防です
この問題が発生するとき
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気温
All temperatures — the virus is active across cassava's entire growing range (18–35°C)
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湿度
Whitefly populations peak at moderate humidity (40–60%); crash in heavy rain
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降雨量
Disease spreads fastest during dry-to-wet season transitions when whitefly populations are highest
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季節
Year-round in tropical regions; worst at onset of rains when whitefly populations explode
Cassava農家向け
For cassava farmers in East and West Africa: Cassava Mosaic Disease is the single greatest threat to cassava production on the continent. It has caused famines in Uganda (1990s) and continues to devastate yields across the Great Lakes region. The ONLY reliable long-term strategy is planting resistant varieties with clean planting material. Do NOT save cuttings from infected fields, even if the plant 'looks okay' — virus can be present without visible symptoms for weeks. If you see mosaic on even one plant, rogue it immediately. Community-level coordination is critical: one farmer leaving infected plants in the field jeopardizes neighbors' crops via whitefly spread. Contact your local agricultural extension office for sources of certified resistant cuttings — many national programs distribute these free or at subsidized cost.
農家もよく尋ねる質問
Can cassava mosaic disease be cured?
No. There is absolutely no cure — no chemical, no organic treatment, no traditional remedy can eliminate the virus from an infected plant. The virus integrates into the plant's cellular machinery. The ONLY responses are: (1) remove and burn infected plants, (2) plant resistant varieties, and (3) control whiteflies to slow spread. Claims of cures are false.
Is it safe to eat cassava from a mosaic-infected plant?
Yes, the virus does not affect human health and cassava from infected plants is safe to eat. However, infected plants produce drastically smaller tubers with lower starch content, so the yield and quality loss is the real problem, not food safety.
Why do resistant varieties sometimes still show symptoms?
Resistant varieties like NASE 14 may show mild, transient mosaic symptoms (especially in young leaves during high whitefly pressure) but they 'recover' — new growth emerges clean, and yield loss is minimal (0–15% vs. 50–100% in susceptible varieties). This is called 'recovery resistance' and is driven by the CMD2 gene.
How can I tell the difference between cassava mosaic and nutrient deficiency?
Mosaic: irregular yellow-green patches following vein patterns, often with leaf distortion/curling, affecting random plants in the field. Nutrient deficiency: uniform yellowing (nitrogen) or interveinal chlorosis (iron/manganese), affecting ALL plants in an area equally, no leaf distortion. If only some plants are affected while neighbors are fine, it's almost certainly mosaic.
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