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.