Diseases of Fruit Plantation Medicinal and Aromatic Crops

Citrus tristeza

Causal organism: Citrus tristiza virus
Symptoms

• Leaf: Chlorosis is the common symptom followed by leaf size reduction, leaves fall and die back of defoliated twigs.
• Stem: Bark eruption and pittings on stem (V shaped depression on the stem and stem twisting occurs.)
• Fruits: In the affected fruits, thicknesss of the rind is increases and, mesocarp decreases.
• Root stocks are susceptible, phloem necrosis is the common symptom, root discoloration and root decay occurs which leads to sudden leaf dropping.
Epidemiology

• Primary source of inoculum: infected plants and cuscuta
• Secondary source of inoculum: Vectors (aphids) (Toxoptera citricida), infected implement used for grafting/budding.
Management

• Use the seedlings developed from seeds for transplanting.
• Use a rough lemon root stock and other scion so as to, protect plants from phloem necrosis.
• Cut and burn the infected parts.
• Replanting with resistant plants in a phased manner.
• Hot water treatment of rootstocks at 450 C for 10-25 minutes.
• Removal of cuscuta and spraying with systemic insecticides like Dimethoate (2ml/lt) controls the aphid vector population.
• Apply recommended dose of N P K and FYM.
• Heat treatment
• Cross Protection: Use pre-immunized seedlings with mild strain of the virus so as to manage the disease and avoid losses.