Diseases of Fruit Plantation Medicinal and Aromatic Crops

Bacterial leaf stripe

Rao and Mohan (1970) reported its occurrence from Tumkur areas of Karnataka state in an endemic form.
Causal organism: Xanthomonas campestris pv. Arecae
Symptoms

• The initial symptoms include 1-4 mm diameter wide, dark green water soaked, translucent, linear lesions or stripes along side and parallel to the mid rib of the leaf let of its other main veins.
• The lesions may develop from any point on the lamina, but more commonly from the base or towards the tip of the leaf let.
• The margin of the lesions is usually straight and well defined, but occasionally it may appear wavy.
• The lesions are covered with abundant bacterial exudates on the lower surface. The exudate is creamy white and slimy.
• On drying, it forms a waxy film or creamy white or yellowish flakes or fine granules or irregular yellowish masses.
• In the advanced stages, the lesions may measure 1cm or more wide and several centimeters long involving the midrib also.
• The affected midrib and veins of the leaflet get discolored and turn black.
• All the leaflets of a leaf may be affected resulting in complete or partial blighting of the leaf and in severe cases the entire crown may get killed, particularly in case of seedlings.


Etiology

• It is soil borne, rod shaped, gram negative bacteria, monotrichous, genetic material DNA reproduced by binary fission.
Epidemiology

• Temperature 26 to 280C, Relative humidity 85-90%, intermittent rainfall, presence of susceptible host favour the disease.
Mode of spread and survival

• The bacterium infects arecanut and other ornamental palms.
• The disease remains aggressive during and after the rainy season and it is of little significance during the hot dry summer months.
• The incidence is high during the months of July - October when the average monthly rainfall is 130mm or more with more than 10 rainy days per month. 3-5 year old palms are highly susceptible to the disease than the older palms.
Management

Cultural control
• Early identification and eradication.
• Use healthy planting materials.
• Antibiotics like tetracycline and its formulations are effective as prophylactic and curative treatments at 500 ppm concentration.
• Stem injection of antibiotics has longer residual effect than foliar spray. Streptocycline 0.05% or copper oxychloride 0.3% spray can also be given.