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Mungbean yellow mosaic India virus and Mungbean yellow mosaic virus ICTV species: Begomovirus vignaradiataindiaense (MYMIV) and Begomovirus vignaradiatae (MYMV); horsegram yellow mosaic virus is also involved · formerly or also: MYMIV, MYMV, HgYMV
Yellow mosaic is the most destructive disease of mung bean and black gram in South and Southeast Asia, and a serious disease of soybean, cowpea and other legumes there. Leaves develop bright yellow patches that spread until whole plants turn yellow, and plants infected young produce few or no pods. It is caused by several closely related begomoviruses spread by the whitefly Bemisia tabaci. Resistant varieties are the main defence.
Yellow mosaic of mung bean, black gram and soybean is caused by Mungbean yellow mosaic India virus and Mungbean yellow mosaic virus, a virus (begomoviruses with single-stranded DNA genomes), spread by whiteflies (order Geplafuvirales, family Geminiviridae).
Older or alternative scientific names: MYMIV, MYMV, HgYMV.
Mainly South and Southeast Asia. Mungbean yellow mosaic India virus dominates in northern, central and eastern India, Pakistan, Bangladesh, Nepal and Vietnam; mungbean yellow mosaic virus in western and southern India, Thailand and Indonesia. Related legume yellow mosaic begomoviruses occur elsewhere in the tropics.
| Region | Status |
|---|---|
| South Asia | Widespread; the main constraint on mung bean and black gram |
| Southeast Asia | Present in Thailand, Indonesia, Vietnam and nearby |
| Other tropical regions | Related legume yellow mosaic viruses present; these species mostly absent |
The viruses are 'twinned' particles detected by PCR; their two genome parts (DNA-A and DNA-B) are often accompanied by mixed infections. They are transmitted by adult whiteflies (Bemisia tabaci, cryptic species Asia II 1 and Asia II 8 in India) in a persistent, circulative way, not through seed or by touch.
| Crop stage | What you see |
|---|---|
| Seedling and early vegetative | Small irregular yellow specks on young leaves that enlarge into bright yellow and green mosaic patches; plants infected this early are stunted. |
| Vegetative to flowering | New leaves increasingly yellow until some are entirely yellow; leaves may be smaller and slightly crinkled; flowering reduced. |
| Pod formation | Few, small, deformed pods with shrivelled seeds, sometimes with yellow mottling on pods; late infections affect only upper leaves. |
Whiteflies acquire the virus from infected crops and weeds and carry it to new plantings. Plants infected in the first three to four weeks suffer most. The virus survives between seasons in legume weeds, volunteer plants and overlapping crops, and whitefly populations build on other crops nearby such as cotton and vegetables.
| Stage | Duration | Notes |
|---|---|---|
| Acquisition by whitefly | From about 10-30 minutes of feeding; efficiency rises with time | Adults and nymphs feed on phloem. |
| Latent period in the whitefly | Several hours | Virus circulates through the insect. |
| Transmission | From minutes of feeding; whitefly remains infective for days | Persistent, circulative. |
| Symptom development | About 1-2 weeks | Yellow specks on young leaves. |
Spread follows whitefly abundance, which is greatest in warm, dry periods such as the spring and summer crops of mung bean in South Asia.
Spread continues while infective whiteflies and susceptible legumes are present.
High whitefly numbers, warm dry weather, susceptible varieties, late sowing into existing whitefly populations, overlapping legume crops and weed reservoirs, and nearby whitefly-heavy crops such as cotton.
There is no economic threshold for the virus, because a few infective whiteflies on young plants can cause heavy losses. Management is preventive and starts with variety choice and sowing date.
Thresholds are local. They depend on crop price, control cost, variety and natural-enemy activity, so use the figure your local extension service publishes where one exists.
Yield losses range from small, with late infection, to 80-100% when susceptible varieties are infected in the first weeks; seed quality also falls. The disease is a major reason for low mung bean and black gram yields in South Asia.
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 (seed treatment and early sprays) can slow spread when combined with resistant varieties. What is registered differs by country and changes over time; follow the label and your local plant-protection authority.
| Scheme | Group | Mode of action | Notes |
|---|---|---|---|
| IRAC | 4A | Nicotinic acetylcholine receptor competitive modulators (neonicotinoids), seed treatment against the vector | Early protection; resistance in whiteflies is widespread. |
| IRAC | 9B | Chordotonal organ TRPV channel modulators, against the vector | Feeding inhibitor. |
| IRAC | 16 | Inhibitors of chitin biosynthesis, type 1, against vector nymphs | Selective. |
Mung bean and black gram are the most damaged; soybean, cowpea, moth bean, horse gram, common bean, lablab and pigeon pea are also infected, as are several leguminous weeds that act as reservoirs.
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.