What is Citrus Canker?
It is a gram-negative, rod-shaped bacteria which affects almost all citrus crops. It is more dangerous when warm weather is accompanied by rain.
Susceptibility- Citrus fruits vary in their susceptibility to canker. Grapefruit and Mexican limes are highly susceptible, sweet oranges and lemons are moderately susceptible, while mandarins are moderately resistant.
Causal organism- Xanthomonas axonopodis pv. Citri
Symptoms-
The disease creates lesion on leaves, twigs, petioles, branches, fruits, fruit stalks and thorns.
- Leaf – Lesions on leaf appears of size ranging from 2 – 10 mm having a concentric circle on the underside of the leaf. These lesions are usually surrounded by water-soaked margins with yellow halo. The halo becomes dark brown or black at maturity. The lesions can be seen on both side of the leaf. The center of the lesions will be corky and volcano or pimple like point on the underside of the leaf. At maturity the upper side of the lesions may have a shot hole appearance.
- Twigs- Initially the lesions appear water-soaked at first and later turn brown. These pustules eventually become corky and girdled.
- Fruit – The symptoms is similar to the leaf ranging from 1-10 mm in size. Larger lesions usually penetrate a few millimeters into the rind. Fruit lesions may vary in size and may coalesce. Fruit lesions consist of concentric circles. On some varieties these circles are raised with a rough texture on other varieties the concentric circles are relatively flat like the surface of a record. The middle of the lesion will be corky in texture with a volcano or pimple like point.
Fig- Symptoms of Citrus canker on leaves and fruits
Source – USDA (idtools.org)
Mode of Spread:
- Splashes of rain
- Open wounds
- Damage wounds by citrus leaf miner
Reason of severity-
The disease is more severe due to prevalence of temperature ranging from 20-35 0C and high humidity
Management-
| Cultural Practices | Chemical Control |
| Prune and burn down the infected parts of plant prior monsoon. | Apply Copper fungicide on the pruned portion.Precautionary spray: Before the monsoon prevails spray Copper Oxychloride 2 gm per liter water.Spraying Copper oxychloride @ 2g per liter + streptocyclin @ 0.4 gm/ltr water 2-3 times at an interval of 15 days will check the infection of disease after the end of monsoon. |
Sources –
Book – Darjeeling Orange : Its Cultivation & Management.
