Diseases of fruit plantation medicinal and aromatic crops (2+1)

Bacterial leaf spot

Causal Organism: Xanthomonas campestris pv. beticola (Asthana and Mahmud)
Symptoms

• The first symptoms of the disease in affected orchards are diminutive.
• Pale yellow spots, rapidly turning dark purple appear along or between the veins on either leaf surface.
• The spots in former positions are roughly circular or angular while in latter, they are irregularly elongated or branched like fern leaves.
• Only in case of advanced decay, the lesions are visible on both the surfaces. The infected leaves gradually turn yellow and fall.
Life cycle
Etiology

• The bacteria are Gram–ve, monotrichous, rod shaped, single celled and aerobic bacteria.
• Primary source of inoculum: Bacterial cells in infected plant debris.
• Secondary source of inoculum: Air borne bacterial cells
• Spread: Through water splash borne and air borne
Epidemiology

• The bacteria require 30-32oC temperature, relative humidity 80-85%, cloudy weather, intermittent rainfall and susceptible hosts for infection.
• The bacteria survive in infected plants, spread through rain splash and air borne bacterial cells and enter through wounds are hydathodes.
Management

• Neem formulation spray 0.3% during the month of Oct-Nov. It will also reduce the nematode population when applied through irrigation water.
• Control the disease by irrigating the garden a week before planting with Bordeaux mixture ( 1%) Spray streptomycin or neomycin @ 2000 ppm.
• Cut and burn the affected plant parts. Vacitracin @ 2000 ppm & Polymycin @ 1000 ppm effectively control the leaf spot. Foliar spray of Azadirachta indica extracts @ 3.0 % is also affective.