PATH 372 Diseases of Horticultural Crops

Shallow necrotic spots on the tubers result from infections through lenticels
Rotting tissue is usually odorless in the early stages of decay, but develops a foul
odor as secondary organisms invade infected tissue.
Soft rot also infects wounded stems and roots
Survival and spread
Survive in diseased and contaminated tubers
Spread through contaminated soil, tubers and maggot flies
Favourable conditions
High humidity (94 – 100%)
Temperature (21 – 29 0 C)
Late blight and Fusarium tuber rot infections predispose soft rot
Management
Remove all debris from warehouses and disinfect the walls with formaldehyde or
copper sulphate
Avoid wounding of plants and storage organs
Products to be stored should be dry, and the humidity and temperatures of
warehouses should be kept low
Crop rotation with cereals
Crop should be planted in well drained areas and at sufficient distances to allow
adequate ventilation
Insect control
Dip cut seed pieces of potato in a solution of Streptocycline 100ppm and CuSo4
40ppm for 30 min
5) Brown rot – Ralstonia solanacearum
First bacterial disease reported in India
First recorded in 1891 from Pune district of Maharashtra
Also referred as bacterial wilt or ring disease or bangle blight
Occurs in Deccan and Central plateau, Assam, West Bengal, Orissa, hills of Uttar
Pradesh and Nilgiris
Symptoms
Wilting, stunting and yellowing of foliage followed by collapse of entire plant
Browning of xylem in vascular bundles
Stems, petioles of the lower leaves and roots become brown and on cutting of
infected materials slimy mass of bacteria oozes out
Brown ring is formed in the tubers due to discolouration of vascular bundles (ring
disease)
Formation of pockets or cavities around vascular bundles in the pith and cortex
When pressed slimy bacterial ooze emerge.
The tubers may rot at harvest or during storage.
Survival and spread
Survive in infected soil and seed tubers
Spread through wind blown soil and water
Infection occurs through wounds
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