About Lesson
Die-Back of Rose
Causal Organism: Diplodia rosarum
Sub-division: Deuteromycotina
Symptoms:
- Infection starts from pruned surfaces of twigs.
- Affected portion turns brown to dark brown or black.
- Twigs dry from the tip downwards.
- Older plants and neglected bushes are more frequently affected.
Disease Cycle:
- Primary Infection: Pycnidia present in dead twigs.
- Secondary Infection: Conidia spread through irrigation water.
Favorable Conditions:
- Cool, moist weather.
- Old and neglected plants are more susceptible.
Management:
- Remove and destroy diseased twigs carefully.
- Protect cut ends after pruning with chaubattia paste.
- Spray Copper oxychloride @ 0.3% in early September and late October.
- Resistant Varieties: Blue Moon, Red Gold, Summer Queen.
Powdery Mildew of Rose
Causal Organism: Sphaerotheca pannosa var. Rosae
Sub-division: Ascomycotina
Symptoms:
- Grayish powdery fungal growth on leaves.
- Rolling of leaf margins during sprouting season.
- Affected leaves become curled and distorted.
- Infected floral parts turn discolored, dwarfed, and dry.
Disease Cycle:
- Primary Infection: Ascospores.
- Secondary Infection: Wind-borne conidia.
Favorable Conditions: Cool and dry climate.
Management:
- Collect and destroy infected plant debris.
- Four sprays with Wettable Sulphur @ 0.3%, Carbendazim @ 0.1%, or Dinocap @ 0.1% at 10-day intervals.
- Resistant Varieties: Ashwini, Ambika, Angeles, American Pride, Surabh.
Black Spot of Rose
Causal Organism: Diplocarpan rosae (Perfect stage: Marssonina rosae)
Sub-division: Ascomycotina
Symptoms:
- Dark brown to black spots with fringed borders on leaves.
- Infected leaves turn brown and fall off.
- Fungus can also infect stems and flowers.
Disease Cycle:
- Primary Infection: Pycnidia or ascospores in infected plant debris.
- Secondary Infection: Wind-borne conidia.
Management:
- Collect and destroy affected parts.
- Spray Carbendazim @ 0.2% at weekly intervals from sprouting until new foliage appears.
- Avoid excessive shade and irrigation.
- Resistant Varieties: Bebe Bune, Coronado, Grand Opera, Sphinx.
