Study of Bacterial diseases in plants
1) Citrus canker
Disease Name: Citrus canker
Causal organsim/Pathogen: Xanthomonas citri
Host: Citrus Plant
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| Citrus canker |
Symptoms:
- The citrus canker is a bacterial disease caused by Xanthomonas citri.
- The canker occurs on leaves, twigs, branches and fruits.
- the lesions first appears on leaves.
- The spot develop first on lower surface of leaves.
- In in beginning lesion will be small, round and watery.
- The spot become rough dark black corky.
Etiology:
The bacteria are transmitted by wind, rain and insects especially leaf mites. On penetration into the host, the bacteria multiplies in the inter cellular spaces. It dissolves the middle lamella and establishes in the cortex.
Control Measures:
- The infected trees must be removed and burnt.
- disease free nursery stock should be planted.
- Purning of diseased twigs and leaves during dry season.
- Spraying the neem cake at the rate of 7 kg per acres.
Disease name: Angular Leaf Spot of Cotton
Causal Organism/Pathogen: Xanthomonas axonopodis pv. malvacearum.
Host: Gossypium herbaceim/Cotton Plant
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| Angular Leaf Spot of Cotton |
Symptoms:
- It is a bacterial disease, caused by the bacteria Xanthomonas axonopodis pv. malvacearum.
- Under favorable condition, infection may spread from the leaf on the petiole and then to the main stem.
- In older plants, the lesions can girdle the main branches causing them to break, with the loss of leaves and fruiting branches. This phase of the bacterial blight syndrome is known as Black arm disease.
It is a seed borne disease. Plant debris and seed sown infected seeds also carry the infection from one season to another season. The pathogen is carried by wind. The main source of primary infection is seed.
Control Measures:
- Removal and destruction of disease debris and collateral hosts, crop rotation.
- Seeds are treated with Agrosan GN and Cerasan
- Cultivation of disease resistant varieties
- Deep ploughing after harvest reduces the survival of pathogen.
