PATH 372 Diseases of Horticultural Crops

1. Use of disease free planting material and prophylactic spray of insecticides and
fungicides.
2. Pruning of diseased parts along with basal 15-20 cm apparently healthy portions.
3. Spray Captan (0.2%) or Benomyl (0.1%).
4. Spray napthelene acetic acid (NAA) 200 ppm during first week of October.
4) Bacterial leaf spot: Pseudomonas mangiferae- indicae
Economic importance: The first description of bacterial leaf spot was given by Patel et
al in 1948 from Maharashtra. In India the disease occurs in Delhi, Tamil Nadu and other
states
Symptoms:
Symptoms are seen on leaves and fruits.
On the leaves initially slightly water soaked yellowish, translucent irregular spots
are formed towards leaf tip which enlarge soon and become dark brown with a
yellow halo.
These dark spots are limited by veins and become angular resulting in cankerous
raised lesions.
Spots appear all over the lamina.
Under high humid conditions these spots fuse, leaves turn yellow and drop down
prematurely.
Longitudinal cracks develop on petioles.
On green twigs, dark lesions of infection spread to inflorescence stalks.
When fruits are attacked, water soaked lesion develop and turn dark brown to
black.
The affected fruits become yellow with deep cracks severely affected fruits are
shed prematurely.
Disease cycle: Primary infection is through infected leaves, branches, and fruits.
Secondary infection occurs by wind driven rain and rain splash.
Management:
Forthrightly spray of 1% B.M. or Agrimycin - 100 or Paushanycin or Plantomycin
(200ppm) or Streptomycin
Resistant variety: Bombay green
5) Sooty mould: Capnodium ramosum
Symptoms:
Black encrustation seen on upper surface of the leaves affecting the
photosynthetic activity.
Superficial growth of the fungus on the flowers, both tender and old leaves, stem
and fruits.
Black encrustation forms on the fruits; appearance is lost yielding low price.
Pathogen grows and thrives on the sugary or honey dew secretions of plant
hoppers.
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