Black spot of Rose

Black spot of Rose

1. BLACK SPOT OF ROSE STUDENT COURSE TEACHER Karthick M.S Dr. Parthasarathy . S ID.NO:2015021055 Asst. Prof. (Plant Pathology)

2. Disease name: Black spot of Rose Pathogen name: Anamorph :  Marssonina   rosae . Teleomorph :   Diplocarpon rosae .

3. SYSTEMATIC POSITION Kingdom : Fungi Phylum : Ascomycota Class : Leotiomycetes Order : Helotiales Family : Dermateaceae Genus : Diplocarpon Species : D.  rosae

4. Significance: The disease is found everywhere rose plant are planted, typically in epidemic proportion. The water borne dispersal methods allow it to infect a plethora of plants every growing season and increases the overall incidence of disease. Diplocarpon rosae does not kill the rose itself, it is known to completely defoliate the leaves of plant.

5. PATHOGEN DESCRIPTION: Acervuli bear the hyaline two celled fusiform conidia. Perithecium bears the asci which contains 8 ascopores .

6. SYMPTOMS: Black spots, one-tenth to one-half inch in diameter, develop first on upper leaf surfaces. Areas adjacent to the black spots turn yellow and leaves drop prematurely, usually beginning at the bottom of the plant and progressing upward. Less commonly, raised purple-red blotches develop on immature wood of first year canes. These spots may later become blackened and blistered.

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8. MODE OF SPREAD: Primary spread : Through Ascospores from perithecia . Secondary spread : Wind borne conidia. MODE OF DISPERSAL: The fungal spores germinate in the spring and are disseminated by splashing water.

9. FAVOURABLE CONDITION: Fungal spores on the leaf surface must be continuously wet for at least seven hours for infection to occur . Once infection is established, the fungus will develop fruiting bodies called acervuli in black lesions which, in turn, produce spores that splash to new tissue, spreading the disease.

10. Management: Remove diseased leaves.  Keep the foliage dry . Spray chlorothalonil  ( Daconil ),  mancozeb or maneb .   Limit the disease by growing roses in locations where they receive morning or, preferably, all day sun.