Diseases of Fruit Plantation Medicinal and Aromatic Crops

Powdery mildew of citrus

Causal organism: Oidium tingitaninum
Symptoms

• Whitish powdery growth appears on young leaves & twigs. In infected leaves get distorted and defoliated in severe conditions.
• Infected twigs exhibit characteristic die back symptom.
• Young fruits are also covered by whitish powdery mass of the fungus and drop prematurely resulting in poor yield.
Etiology and Spread

• Comparatively cool and moist fields are prone to disease development.
• Damp mornings with only few hours of sunshine favours onset of the disease.
• The fungus is an ectoparasite and absorbs food material from the epidermal cells of leaf through haustoria.
• It is a wind- borne disease. Septate mycelia, barrel shaped conidia borne in chains, ectophytic, sub epiderml haustoria, external mycelia.
• PSI: Dormant mycelia.
• SSI: Air borne barrel shaped conidia.
Life cycle

• Dormant mycelia present in the infected parts germinate and produce oidea during congenial conditions.
• On maturity, barrel shaped conidia are released, which are air borne and find a host.
• Infection takes through sub- epidermal haustoria and plant starts producing powdery growth comprising of oidea.
• Oidia is an asexual fruiting body of the powdery mildew and barrel shaped conidia are borne in chains on oidiophores.
• They release and land on their respective host through air.
• Infection process continues asexually
Management

• Prophylactic measures: cloudy warm weather, spray
• Aerial spray: Bavistin @1.25gm/lt ,calixin @ 1ml/lt andWettable sulphur@ 3gm/ lt
• Wider spacing between plants
• Avoid high density planting
• Avoid excess N application in the soil
• Provide recommended dose of potassium