Horsegram yellow mosaic virus (HgYMV)
Bright yellow-and-green leaf mottling spread by the whitefly — one of the two biggest reasons a horse gram crop underperforms in India.
- Pathogen
- Virus (begomovirus, HgYMV)
- Spreads by
- Whitefly (Bemisia tabaci)
- Favoured by
- High whitefly numbers; nearby infected pulses
- Main risk
- Stunting and heavy pod-set loss if infected early
Overview
Horsegram yellow mosaic virus (HgYMV) is a begomovirus — a distinct species from the yellow mosaic virus that affects moong, urad and soybean, though it is spread the same way and looks similar in the field. It is carried from plant to plant by the whitefly (Bemisia tabaci), not by seed or touch. Infected leaves develop scattered bright yellow patches that spread into a yellow-and-green mosaic; badly affected leaves turn almost fully yellow.
Screening of horse gram germplasm has found a wide range of reactions, from highly resistant to highly susceptible lines, and yield loss on a susceptible plant infected early can run very high — which is exactly why several of the newer ICAR-CRIDA releases (CRHG-4, CRIDA-18R, CRHG-19) are specifically bred and marketed for their HgYMV tolerance. Since the virus itself cannot be sprayed away, control means controlling the whitefly and reducing how much virus is sitting in and around the field to begin with.
How to identify it
- Scattered bright yellow patches on young leaves that spread into a yellow-and-green mottled pattern.
- Badly affected leaves turn almost fully yellow and the plant looks pale from a distance.
- Plants infected early are visibly stunted and set fewer, smaller pods.
- Symptoms can be confused with a nutrient problem at a glance — check for the mottled (not uniform) yellowing and for whitefly on the underside of leaves to tell the two apart.
What causes it and when
- A begomovirus carried only by the whitefly (Bemisia tabaci) — it does not travel in seed or by simple contact between plants.
- Whiteflies pick up the virus feeding on an infected plant and inject it into the next healthy plant they feed on, so spread tracks whitefly numbers, not weather alone.
- Nearby infected pulse crops, self-sown volunteer plants and some weeds can carry the virus over between seasons.
- The earlier in the crop's life infection happens, the worse the stunting and pod loss.
Cultural & organic control
- Choose a variety bred for HgYMV tolerance where seed is available — CRHG-4, CRIDA-18R and CRHG-19 are documented as tolerant in ICAR-CRIDA trials, and this is the single most reliable control.
- Sow with the recommended window for your area rather than very late, so the crop is past its most vulnerable young stage before whitefly numbers typically peak.
- Rogue out (pull and destroy) badly infected plants seen early, before whiteflies can spread the virus further from them.
- Clear volunteer horse gram plants and nearby weed hosts between seasons so the virus has nowhere to carry over.
Chemical (vector) control
- Because the virus itself cannot be killed by any spray, every chemical measure here targets the whitefly that carries it.
- Yellow sticky traps help monitor and reduce whitefly numbers in and around the field.
- A CIB&RC-registered insecticide against whitefly, used judiciously and rotated between different modes of action, controls the vector when numbers build up — ask your local KVK for the current recommendation.
- Avoid routine, calendar-based spraying that also kills the natural predators that otherwise help keep whitefly numbers down.
Prevent it coming back
- In areas with a history of HgYMV, make a tolerant variety the default choice rather than the fallback.
- Keep field borders and bunds free of volunteer legumes and weed hosts that carry the virus between seasons.
- Watch whitefly numbers from early crop growth onward, since early infection does by far the most damage.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
My horse gram leaves have yellow and green patches — is this the same disease as YMV in moong?
It looks similar and spreads the same way, but horsegram yellow mosaic virus (HgYMV) has been characterised as its own distinct begomovirus, not the same organism as the yellow mosaic virus recorded on moong, urad and soybean. Both are managed the same way in practice — by controlling the whitefly that carries them and removing infected plants and weed hosts.
Can I spray something to cure a horse gram plant that already has HgYMV?
No — once a plant is infected, no spray removes the virus from it. The only options for an already-infected plant are to rogue it out to stop it being a source for whiteflies to spread from, or to accept the loss on that plant while protecting the rest of the crop by controlling the whitefly vector.
Which horse gram varieties tolerate this virus?
ICAR-CRIDA's CRHG-4, CRIDA-18R and CRHG-19 are documented in trials as tolerant to horsegram yellow mosaic virus, alongside other traits like powdery mildew or mite tolerance depending on the variety. Where seed of one of these is available for your area, it is a more reliable defence than any in-season spray, since the virus itself cannot be treated once a plant is infected.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.