Rose black spot is a fungal disease of plants that causes purple or black spots on the leaves, which often turn yellow and drop early. This reduces photosynthesis, so less glucose is made and the growth of the plant is affected. It is spread by water or wind, and is treated with fungicides and by removing and destroying affected leaves.
Rose black spot is a fungal disease of plants. Purple or black spots develop on the leaves, which often turn yellow and drop early.
It affects the growth of the plant because photosynthesis is reduced. Less photosynthesis means less glucose is made for growth.
It is spread in the environment by water or wind.
Treatment
Using fungicides.
Removing and destroying the affected leaves.
Exam tip:
The leaves are removed and destroyed, not just removed. Destroying them stops the fungus spreading to other plants.
Written and checked against the AQA GCSE Biology (8461) specification · Updated October 2026
Frequently asked questions
How do pathogens spread?
Pathogens spread by direct contact, by water or by air. HIV and gonorrhoea spread by sexual contact, and HIV also by the exchange of body fluids such as blood. Measles spreads in droplets from sneezes and coughs, and rose black spot by water or wind. Salmonella spreads in food, and malaria is carried by mosquitos.
How do white blood cells fight infection?
White blood cells fight infection in three ways. Some engulf and digest pathogens, which is called phagocytosis. Others produce antibodies, which target a particular pathogen and help to destroy it, and antitoxins, which neutralise the toxins released by pathogens. This is the immune system, which acts when a pathogen gets past the non-specific defences.
How do vaccines work?
Vaccines work by introducing small quantities of dead or inactive pathogen into the body, which stimulates white blood cells to produce antibodies. If the same pathogen enters the body later, the white blood cells respond quickly to make the correct antibodies, so the pathogen is destroyed before it causes illness. A vaccine does not contain antibodies itself.
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