Bud necrosis / spotted wilt (tospovirus)
Ringspots and necrotic streaks leading to bud and tip death, stunting and deformity — a thrips-spread virus stopped by managing thrips.
- Pathogen
- Tospovirus (bud necrosis / spotted wilt)
- Spreads by
- Thrips
- Favoured by
- High thrips numbers; infected sources
- Main risk
- Bud/tip death; severe stunting; plant killed
Overview
Bud necrosis and spotted wilt are diseases caused by tospoviruses (such as groundnut/peanut bud necrosis virus and related tospoviruses), spread by thrips. Early symptoms are small chlorotic spots and concentric ringspots on the leaves; these develop into necrotic (dead brown) spots, streaks and lesions on leaves, petioles and stems, and — characteristically — the terminal bud and growing tip die back (bud necrosis). Affected plants are stunted, with small, deformed, mottled leaves and axillary shoots, and early-infected plants are severely dwarfed, deformed and often killed.
The virus is acquired by thrips as larvae feeding on infected plants and then transmitted by the adult thrips as they feed, so spread is tied entirely to thrips activity and movement (it is not seed-borne in the usual sense). It is worse where thrips numbers are high and infected crop and weed hosts are around, and early-season infection is by far the most damaging. Because the virus cannot be cured, management combines early thrips management, roguing infected plants, healthy vigorous stands, and removing weed hosts.
How to identify it
- Small chlorotic spots and concentric ringspots on the leaves early on.
- Necrotic (dead brown) spots, streaks and lesions on leaves, petioles and stems.
- Death of the terminal bud and growing tip (bud necrosis), with stunting and small, deformed, mottled leaves.
- Early-infected plants severely dwarfed, deformed and often killed; damage tracks thrips activity.
What causes it and when
- Tospoviruses (e.g. groundnut/peanut bud necrosis virus), transmitted by thrips.
- Thrips acquire the virus as larvae on infected plants and transmit it as adults — spread is tied to thrips activity and movement.
- Worse where thrips numbers are high and infected crop and weed hosts are nearby.
- Early-season infection is by far the most damaging; late infection matters much less.
Cultural & organic control
- Manage thrips early, especially in the nursery and young crop, before the virus spreads.
- Grow tolerant/resistant varieties where available and use recommended spacing and healthy, vigorous stands.
- Rogue out and destroy infected plants early, and remove weed hosts that carry the virus and thrips.
- Adjust sowing time where advised to escape peak thrips, and use barrier/border crops.
Chemical (vector) control
- The virus cannot be sprayed — target the thrips vector early to reduce spread, using CIB&RC-registered insecticides judiciously with traps and natural enemies.
- Focus vector control on the early, most vulnerable stage; killing thrips later does not cure infected plants.
- Combine thrips management with roguing, tolerant varieties and weed-host removal.
- Confirm the current thrips-management schedule for your crop with your local KVK.
Prevent it coming back
- Make early thrips management, tolerant varieties and prompt roguing the routine.
- Remove weed hosts and volunteers, and adjust sowing time to avoid peak thrips where advised.
- Keep stands healthy and vigorous, and use barrier crops to slow thrips movement.
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 groundnut/sunflower has ringspots and dead streaks and the growing tip has died. What is it?
Chlorotic spots and concentric ringspots developing into necrotic streaks, with death of the terminal bud and growing tip and stunted, deformed plants, are bud necrosis / spotted wilt, a tospovirus spread by thrips. Early-infected plants are severely stunted and often killed. The virus cannot be cured — manage thrips early (especially in the young crop), rogue infected plants, use tolerant varieties, and remove weed hosts that carry the virus and thrips.
How do thrips spread bud necrosis?
Thrips pick up the tospovirus as larvae feeding on infected plants, and then transmit it as adults when they feed on healthy plants. So the whole spread of bud necrosis is tied to thrips — their numbers and movement decide how far and fast it goes. That is why control targets thrips early, before they spread the virus through the crop, and combines that with roguing infected plants and removing the weed hosts where thrips and the virus persist.
Why is early infection so much worse with bud necrosis?
Because a plant infected early — as a seedling or young plant — has the virus kill its growing bud and stunt and deform it for the rest of its life, so it is often a total loss. A plant infected late, near maturity, has already made most of its growth and yield and loses far less. That is why control concentrates on protecting the nursery and young crop by managing thrips early, rather than reacting once ringspots and bud death are widespread.
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.