What is Citrus Scab?
It is a fungal disease that results in brownish, warty scabs that appear on the rind. While it does not make the fruit inedible, it does reduce marketability in most cases.
Susceptibility– Lemon, Rough lemon, Rangpur lime and mandarin are more susceptibility. Grapefruit, Sweet Oranges and Pomelo moderately susceptibility.
Causal organism– Elsinoe fawcettii in all cultivars while E. australis is known to infect only in sweet orange & sour orange.
Symptoms-
- The disease damage leaves, fruits and twigs.
- In leaves it is characterized by wart-like, small, raised pustules usually underside of leaves while at opposite appears as circular depression with pink- red center
- Later the leaves become stunted, wrinkled with irregular torn margins.
- Similar symptoms are also shown on twigs which later twigs die.
- In fruits the symptoms appear as whitish, raised, circular, scabrous growth which change to greyish colour affecting quality of fruit, decreasing the fruit size and eventually cause fruit drop.
Mode of spread-
- The disease act as a host on the lesion of affected fruits, leaves so these should be disposed properly.
- The pathogen survives in off season as ascospores and spreads through spores.
- Spores of the fungus are spread in the orchard by rain, overhead irrigation and some dry spore through wind.
Reason of severity-
- When the surface is wet and the temperature is around 16 – 23℃, the fungus can readily can invade the young leaves, tender twigs and developing fruit to establish infection.
Management–
| Cultural Practices | Chemical Control |
| Proper sanitation in orchard.The diseased leaves, twigs and fruits should be collected and destroyed. | After the pruning the plant should be sprayed with Copper Oxychloride 50% WP @ 2 g per liter of water Spray Carbendazim 50% wp @ 2g per liter Mancozeb 75% WP @ 2g per liter of water also help in controlling the disease. |
Source-
Book – Field Problem of Fruit Crops, Dr. Amarjit Singh & Dr. Chander Mohan, PAU, Ludhiana
