Corynespora leaf fall
Fishbone-patterned dark veins and brown papery lesions on rubber leaves, causing repeated off-season defoliation — worst on RRII 105, and managed mainly by clone choice.
- Pathogen
- Fungus (Corynespora cassiicola)
- Spreads by
- Air-borne spores; active much of the year
- Favoured by
- Warm humid weather; susceptible clones (RRII 105)
- Main risk
- Repeated off-season defoliation and loss of vigour
Overview
Corynespora leaf fall is caused by the fungus Corynespora cassiicola. On rubber it produces a characteristic "fishbone" or "railway track" pattern — dark, blackened veins radiating from a lesion — along with brown, papery, often shot-hole lesions on both mature and young leaves. Heavily infected leaves fall, and the tree refoliates and is defoliated again, outside its normal annual wintering period.
It has become a serious and spreading problem on the widely planted clone RRII 105 in several tracts, and some other clones are far more susceptible than the RRII 400-series. Unlike abnormal leaf fall it can attack through much of the year, not just the monsoon, which makes repeated spraying of tall mature rubber difficult and costly. Because of this, the main defence is clone choice — avoiding highly susceptible clones where the disease is established, and planting tolerant clones in new areas.
How to identify it
- A "fishbone" or "railway track" pattern — darkened, blackened veins spreading out from a lesion on the leaf.
- Brown, papery lesions, sometimes with the dead centre falling out to leave a shot hole, on mature and young leaves.
- Repeated leaf fall and refoliation outside the tree's normal annual wintering period.
- Worst on RRII 105 and other highly susceptible clones.
What causes it and when
- The fungus Corynespora cassiicola, spread by air-borne spores.
- Active through much of the year in warm, humid conditions — not confined to the monsoon like abnormal leaf fall.
- Clone susceptibility varies widely; RRII 105 is badly affected in several Indian tracts, while the RRII 400-series clones are more tolerant.
Clonal & cultural control
- Clone choice is the main defence — avoid highly susceptible clones where Corynespora is established, and plant tolerant RRII 400-series clones (RRII 414, RRII 417) for new areas.
- Keep trees vigorous with balanced nutrition so they can carry and refoliate.
- Follow the current RRII advisory for your region, as the disease situation and clone recommendations are changing.
Chemical control
- Fungicide sprays as recommended by RRII can help on affected blocks, but repeated spraying of tall, mature rubber is difficult and expensive, so it is not a long-term substitute for a tolerant clone.
- On nursery and young immature plants, protective fungicide cover is more practical.
- Confirm the current product, dose and timing with your local RRII office.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Varieties to consider
Named seed varieties whose resistance or susceptibility to this problem is documented on their own variety page.
Frequently asked questions
My RRII 105 rubber keeps shedding leaves outside the wintering season. Why?
This is a classic sign of Corynespora leaf fall, a fungal disease that has become serious on RRII 105 in several tracts. Look for the "fishbone" pattern of blackened veins and brown papery lesions on the leaves. It attacks much of the year, not just the monsoon, and repeated spraying of tall trees is impractical — the real fix is to plant a tolerant clone (such as RRII 414 or RRII 417) when replanting.
How is Corynespora leaf fall different from abnormal leaf fall?
Abnormal leaf fall is a Phytophthora disease tied to the wind-driven rain of the monsoon, and is managed by spraying the canopy before the rains. Corynespora leaf fall is caused by a different fungus, can attack through much of the year, shows a distinctive fishbone vein pattern, and is managed mainly by choosing a tolerant clone rather than by spraying.
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.