Citrus Powdery Mildew

Disease of Citrus
By A. Dhanalakshmi

1. CITRUS POWDERY MILDEW STUDENT Ms. A. Dhanalakshmi ID. No. 2015021028 COURSE TEACHER Dr. PARTHASARATHY S Asst. Professor., (Plant Pathology) COLLEGE OF AGRICULTURAL TECHNOLOGY (Affiliated to Tamil Nadu Agricultural University, Coimbatore-3) Kullapuram (Po), ViaVaigai Dam, Theni-625 562

2. CITRUS POWDERY MILDEW Causal organism Acrosporium ( oidium ) tingitaninum (Carter).

3. DISTRIBUTION The disease is common in parts of Asia where it is prevalent in shady, poorly ventilated orchards. There have also been reports from Uganda, Israel, Central and South America and the united states. Citrus powdery mildew is not known to occur in Australia. In India, Nilgiris , Palanis , Wynad and Shevoy hills.

4. SIGNIFICANCE AND HISTORY Severe infection can significantly reduce tree productivity, fruit quality and yield. In India, powdery mildew was first collected from the Nilgiri hills in 1904, and the Edwin Butler identified the fungus as Oidium citri . Devarajan , Naik and ramakrishnan reported that powdery mildew caused by Acrosporium tingitaninum . And also they reported that powdery mildew can be easily controlled by dusting the foliage with Sulphur .

5. ETIOLOGY Comparatively cool and moist fields are prone to development. Damp mornings with only few hours of sunshine favours onset of the disease. The fungus is an ectoparasite , it is a wind borne disease.

6. SYSTEMIC POSITION Kingdom : Fungi Division : Ascomycota Class : Leotiomycetes Order : Erysiphales Family : Erysiphaceae Genus : Oidium Species : O. tingitaninum

7. MODE OF SPREAD: Primary spread: Air borne conidia. Secondary spread: Ascospores from the infected debris.

8. SYMPTOMS Whitish powdery growth appears on young leaves and 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.

9. Leaves Fruit

10. PATHOGEN Hyaline club shaped conidiophore with chain of barrel shaped conidia arranged in basipetal succession. Sexual fruiting body is chasmothecium which bears asci and ascospores .

11. 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 oidia

12. 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.

13. MANAGEMENT Aerial spray: Bavistin @ 1.25gm/ lt , calixin @ 1ml/ lt and Wettable sulphur @ 3gm/ lt. Wider spacing between plants. Avoid high density planting. Avoid excess N application in the soil. Provide recommended dose of potassium.

14. References http://agropedia.iitk.ac.in ecoursesonline.iasri.res.in/mod/page/ view.php?id =9201