3.1.4 - Fungal Diseases

What is rose black spot?

A fungal disease which causes purple or black spots to develop on rose leaves. It reduces the area of the leaf which is available for photosynthesis and causes leaves to turn yellow and drop prematurely.

How is the rose black spot fungus spread?

• Fungal spores are spread by the wind and in water

• Human handling of the plants (vector transmission)

• Leaves brushing against each other

Why is the rose black spot fungus problematic for the plant?

It stunts growth of the plant as photosynthesis is reduced + a lack of chlorophyll means light can’t be absorbed, so glucose isn’t produced. Respiration and protein synthesis rates decrease.

How can the rose black spot fungus be treated?

• Using fungicides

• Destroying infected leaves

What is done to the infected leaves after stripping the plant?

They are burnt