Practise Fungal diseases. 11 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Rose black spot is the fungal disease in the specification. You need to know what it looks like, how it spreads, why it reduces the plant's growth and how it is treated.
Grade by grade
What you need to be able to do, from the first marks up to the top grade.
3
Name a fungal disease of plantsRose black spot is a fungal disease of roses.
4
Describe the symptoms of rose black spotPurple or black spots develop on the leaves, which often turn yellow and drop early.
4
State how rose black spot is spreadIt is spread in the environment by water (e.g. splashing rain) or by wind.
5
Describe how rose black spot is treatedUse fungicides and/or remove and destroy the affected leaves.
6
Explain why black spot reduces growthSpotted, yellow and fallen leaves mean less photosynthesis, so less glucose is made for growth.
7
Explain why infected leaves must be destroyedInfected leaves, including fallen ones, still carry the fungus, which can spread to healthy leaves by water or wind.
Notes
What rose black spot is
A disease of roses caused by a fungus.
Symptoms: purple or black spots develop on the leaves. The leaves often turn yellow and drop early.
How it spreads
The fungus produces spores, which are spread in the environment by water (e.g. rain splashing from leaf to leaf) or by wind.
Spores that land on the leaves of a healthy rose can infect it.
The fungus can survive on fallen leaves, so fallen leaves can be a source of new infections.
Why it reduces growth
The spotted and yellow parts of the leaves have less chlorophyll, and leaves that have fallen off cannot photosynthesise at all.
So the plant carries out less photosynthesis, makes less glucose and grows less.
Treatment
Spray the plant with fungicides (chemicals that kill fungi).
Remove and destroy the affected leaves, including any that have fallen, so the fungus cannot spread to other leaves or plants.
Gardeners often use both methods together.
Antibiotics do not treat fungal diseases: they kill bacteria, not fungi.
Cheatsheet
Rose black spot = fungal disease of roses
Symptoms: purple or black spots on leaves; leaves turn yellow and drop early
Spread: by water or wind
Effect: less photosynthesis → less growth
Treatment: fungicides and/or remove and destroy affected leaves
Fungicide = chemical that kills fungi
How to answer each type of question
Recall: pathogen type, symptoms and spread
1 to 3 marks4
Name the pathogen type: a fungus.
Use the exact symptom words: purple or black spots, leaves turn yellow, leaves drop early.
For spread, give water and wind.
Example. Rose black spot is a disease of rose plants. (a) What type of pathogen causes rose black spot? (b) Describe how rose black spot is spread from one plant to another.
Show the model answer
(a) A fungus (1) (b) By water, e.g. rain splashing spores onto other leaves (1); by the wind carrying spores to other plants (1)
Describe and explain treatments
2 to 4 marks5
Give the two treatments: fungicide and removing and destroying affected leaves.
Explain each: the fungicide kills the fungus; destroying leaves stops the fungus spreading.
Example. Give two ways a gardener could treat roses with black spot. Explain how each way helps.
Show the model answer
Spray the roses with a fungicide (1), which kills the fungus (1). Remove and destroy the affected leaves (1), so the fungus cannot spread from them to healthy leaves (1).
Explain why growth is reduced
3 marks6
Start with the symptoms: spots, yellow leaves, leaves falling off.
Link to less photosynthesis.
Finish with less glucose for growth.
Example. A gardener noticed that roses with black spot grew fewer new shoots than healthy roses. Explain why.
Show the model answer
The leaves have black spots, turn yellow and fall off early (1). So there is less photosynthesis (1). So the plant makes less glucose, which it needs for respiration and to make new cells for growth (1).
Data: testing a treatment
2 to 3 marks7
Percentage = number affected ÷ total × 100.
Compare the treated and untreated groups.
For 'suggest why', think about how the fungus could still reach or survive on the leaves.
Example. A gardener sprayed 40 rose plants with a fungicide and left 40 plants unsprayed. Later, 12 of the sprayed plants and 33 of the unsprayed plants had black spot. (a) Calculate the percentage of plants in each group that had black spot. (b) Suggest one reason why some sprayed plants still had black spot.
Show the model answer
(a) Sprayed: 12 ÷ 40 × 100 = 30% (1); unsprayed: 33 ÷ 40 × 100 = 82.5% (1) (b) Any one from: rain washed off the fungicide; not every leaf was covered; spores kept arriving from unsprayed plants nearby (1)
Shortcuts and memory tricks
The name tells you the symptom: black spots on the leaves, which then turn yellow and fall off.
Fungi → fungicides; bacteria → antibiotics. Match the chemical to the pathogen.
Any plant disease that damages leaves: fewer or less green leaves → less photosynthesis → less glucose → less growth.
Where marks are lost
Saying black spot is caused by a virus or a bacterium. It is caused by a fungus.
Suggesting antibiotics or 'medicine' as a treatment. Use fungicides.
Writing 'remove the leaves' without 'destroy'. Leaves left lying on the ground can still spread the fungus.
Writing 'it stops photosynthesis'. It reduces photosynthesis.
Exam technique
Use the precise symptom words: purple or black spots, leaves turn yellow, leaves drop early.
For 'explain why growth is reduced', always link to photosynthesis and glucose.
If a question gives a fungal disease you have not met, apply the same ideas: spread by water or wind, treated with fungicides and by removing infected parts.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Rose black spot is a disease of rose plants. Give one way that rose black spot is spread.
By water or wind.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy6 marks
Rose black spot is a disease of rose plants.
(a) What type of pathogen causes rose black spot? Tick (✓) one box.[1]
Bacterium
Fungus
Protist
Virus
(b) Describe what the leaves of a rose plant with black spot look like.[2]
(c) Give one way that rose black spot is spread.[1]
(d) Give two ways that a gardener could treat rose black spot.[2]
Show the answer and mark scheme
(a)Answer: Fungus
(b)
purple / black spots on the leaves
leaves turn yellow (and drop off early)
(c)Answer: By water or wind.
(by) water / rain
(by) wind
(d)
spray with a fungicide
remove and destroy the affected leaves
Question 2Medium6 marks
A gardener noticed black spot on some rose bushes. Many of the leaves turned yellow and fell off early.
(a) Explain why rose bushes with black spot grow less than healthy rose bushes.[3]
(b) The gardener collected the fallen leaves from the ground and burned them. Explain why this helps to stop black spot spreading.[2]
(c) Suggest why black spot spreads more quickly in wet weather.[1]
Show the answer and mark scheme
(a)
fewer leaves / less green leaf area / less chlorophyll
(so) less photosynthesis
(so) less glucose for respiration / for making new cells / for growth
(b)
the fallen leaves contain the fungus / spores
burning destroys the fungus, so it cannot be spread (by wind or water) to healthy leaves / plants
(c)
the fungus / spores are spread by water, e.g. rain splashes spores onto other leaves
Question 3Hard5 marks
A gardener must dilute a fungicide concentrate with water before spraying rose bushes. The instructions say the diluted spray should contain 1 cm3 of concentrate for every 200 cm3 of diluted spray.
(a) Calculate the volume of concentrate needed to make 5 dm3 of diluted spray.[2]
(b) Calculate the volume of water needed to make up this 5 dm3 of spray.[1]
(c) Suggest why using a more concentrated mixture of fungicide than the instructions state could damage the rose plants.[2]
Show the answer and mark scheme
(a)Answer: 25 cm3
5 dm3 = 5000 cm3, and 5000 ÷ 200
25 (cm3)
(b)Answer: 4975 cm3
5000 − 25 = 4975 (cm3)
(c)
a highly concentrated fungicide is more likely to be toxic to the plant's own cells, not only to the fungus