Worldwide distribution. In Oceania, Australia, Fiji, New Caledonia, New Zealand, Papua New Guinea. A fungal leaf spot of rose.
Damage: irregular black spots on the leaves with irregular borders, sometimes with yellow halos, causing leaves to yellow and fall. Spots on young stems. Overtime, defoliation leads to weak plants and fewer flowers.
Spread: as spores in wind-blow rain and rain-splash. Survival on fallen leaves or on leaves, bud scales and stems on the plant.
Cultural control: in the nursery - check plants for infection; in the field/garden choose sunny, well-drained site, and space to allow good air circulation; collect and burn fallen leaves, and apply mulch; water frequently, early morning, avoiding overhead irrigation; prune regularly to aid air movement; apply fertilizer little and often; weed; resistant varieties - but if growing susceptible types, mix with those resistant.
Chemical control: minerals (i) sulphur, copper, sodium (or potassium) bicarbonate; botanicals (ii) neem; (iii) microbials - Bacillus subtilis; synthetics iii) protectant fungicides - captan, chlorothalonil, mancozeb or systemic fungicides - triazole or strobilurin.