Diseases of Fruit Plantation Medicinal and Aromatic Crops

Leaf curl

Causal organism: Taphrina deformans (Berk & Tul)

SYMPTOMS


• The disease first appears in early spring as the leaves begin to unfold.
• The leaf blade thickens, midrib turns yellow and curls.
• Finally the infected leaf turns to reddish purple tint.
• The reddish velvety surface of lamina is soon covered with a whitish grey bloom of the fungus on the upper surface.
• Both the leaves and petiole may curl.
• Infected leaves die and drop immaturely.
• Twigs become pale green to yellow, swollen, stunted and exude gummy material.
• Flowers and fruits are also infected and drop prematurely.




ETIOLOGY
Mycelia are intercellular and do not produce ascocarp.
Asci are produced individually and measure 25- 40 x 8 - 11 µm.
Each ascus bears eight ascospores with a diameter of 3 to 7 µm.

EPIDEMIOLOGY
The disease is prevalent in areas where cool, misty spring weather prevails and the dry hot weather hastens defoliation.
PSI: Dormant mycelia in affected stem.
SSI: Air borne conidia.

Life cycle
The pathogen spreads through wind and rain and attacks the leaves as they break bud and fruit begins to develop during cool, wet weather. A single layer of spore-producing tissue develops on the infected plant part, giving the blistered area a white or translucent appearance when fresh. Spores are released from this tissue from late spring to midsummer and remain on twigs and bud scales until following spring season.

Management
Removal and burning of infected shoots reduce spread of the disease.
A dormant spray of Bordeaux mixture (6:10:100) with an adhesive or sticker and a winter spray with Bordeaux mixture (1.2%) before bud burst control the disease.