Fungal Black Spot
Fungal Black Spot, Black Spot
Circular black spots that can reach up to 50mm with a perforated or feathery edge and often with a yellowish halo around the spot. Severe infections will cause the spots to run together and cause a large, black mass.
Infections occur during damp and humid periods and wet conditions are required for the disease to spread.
Leaves turn yellow and drop early
Plant vigour is greatly reduced
With times a plant can loose all it's leaves
Black spots on upper side of leaf occurring from the bottom up of a plant
Always remove or destroy infected leaves immediately and try using Neem oil as a biological treatment.
Anti-fungal applications like Chronos, which contains a imidazole prochloraz zinc complex can be used to treat black spot. Always read the instructions supplied on the packaging.
A healthy plant is less susceptible to problems and diseases. Ensure good air circulation of plants by not planting them close together and pruning often when they become dense. Avoid overhead-watering, especially later in the day and mulch well beneath your plants to reduce water splashing up on leaves. Plant resistant cultivars and last but not least, treat the bush with preventive sulphur spray in spring, before new growth arises. Spores won’t grow on sulphur and you will need to repeat the application after each rain as it will wash off.
The disease is caused by numerous species of fungi affecting many plants.