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
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Last modified: Thursday, 19 January 2012, 4:11 AM