Diseases of Fruit Plantation Medicinal and Aromatic Crops

Scab

Scab of peach

Causal organism: Venturia carpophila
Symptoms

• The disease occurs on fruit, twigs and leaves.
• Circular and dark –olivaceous lesions appear on fruits.
• In severe infection, the individual spots merge and form a uniform, dark olivaceous, velvety blotch.
• A thick or corky layer of cells is produced below the surface of the scabbed region.
• The fruit becomes abnormal in shape and cracks.
• On the twigs, light brown oval lesions are formed which enlarge and turn dark brown.
• Dark brown, long and narrow lesions are noticed on the midrib.


Etiology

• Septate mycelia which remain Dormant
• Primary source of inoculum: Dormant mycelia present in fallen leaves.
• Secondary source of inoculum: Spilocea type of air borne conidia
• Infection takes place in between the cuticle & epidermis.
  
Epidemiology

• Minimum nine hours of leaf wetness period, 17-18°c temperature and susceptible host.
• In fallen leaves normally 200-300 pseudothecia is present and if leaf wetness continues 9 hours, single pseudothecium may produce 800-900 ascospores.
  
Management

• Cut and burn infected plant parts.
• Low- lying fields should be avoided for cultivation.
• Trees should be properly pruned to permit free air circulation.
• Timely application of the standard fungicides like and sprays control the scab.
• Spraying of 5% urea solution to the fallen leaves for early decomposition.
• Chemical spray schedule should be followed for effective control like
a) Silver tip to green tip- Mancozeb @ 4g/litre water
b) Pink bud stage-carbendazin @ 1g/ litre water.
C) Fruit stage-(pea nut stage) – capton @ 3g/ litre water.
d) 40 days before harvest –Hexaconozole @1.5g /litre water.
• Biological agents like Althelia species, Chaetomium globosum should be applied for control.