Set by Dr Phil Taylor.
It is Valentine’s day this month. For those of you who do not celebrate this day (14th Feb), it is a time when cards, flowers and chocolates are often exchanged between partners (or those who you may like to be your partner). There are no diseases of greetings cards, so this month’s quiz is on the diseases of flowers and cacao.
#1. What is causing the mosaic on this rose leaf?
The correct answer is:
Rust infection
Mosaics such as this are frequently associated with viral infection, but that is not always the case. Looking at the upper surface, the go to diagnosis would be virus, but inspecting the lower side reveals the orange pustules which shows the true cause of the mosaic. Another really common mosaic, not due to a viral infection, is cucumber downy mildew.
#2. What has happened to this rose leaf?
The correct answer is:
Fungal infection that has been overrun by bacterial infection.
The black circular regions are infection by the fungal pathogen Diplocarpon rosea which causes “Black spot of roses”. What appears to have happened is that a bacterial pathogen has entered from the tip of the leaf and has overrun two of the three black spot infection sites.
#3. What is the white material on the leaf surface?
The correct answer is:
Spray residue:
The leaves of these roses were sprayed with tetracycline, to prevent bacterial infection, and Thiophante methyl, to prevent fungal infection: the residue can clearly be seen. Spraying crops with antibiotics is a practice which should be discouraged.
#4. What is this pest attacking this rose bud?
The correct answer is:
Aphids:
A very common pest characterised by: the pear-shaped soft body, obvious legs and, normally, a lack of wings on most of the population.
#5. Which mineral is this rose plant lacking?
The correct answer is:
Manganese:
It isn’t really possible to tell which nutrient is lacking here (could have been several), but hopefully you were able to dismiss all the other options.
#6. What has damaged this rose tip?
The correct answer is:
Thrips:
Thrips can get into the apex of a plant and the feeding may cause the developing leaves to appear distorted once they have expanded.
#7. What is attacking this dahlia flower?
#8. What is the cause of the spectacular rings on these dahlia leaves?
#9. This is black pod disease on cocoa. It is one of the few examples of above-ground infection of which kind of pathogen?
The correct answer is:
Phytophthoras:
Late blight on potato and tomato is an extremely common disease, but there are relatively few other common examples of Phytophthora attacking above ground, they are mostly pathogens of roots and lower stems. Here we see Phytophthora palmivora attacking the cocoa pods.
#10. Leaf edge necrosis seen here on cocoa is a classic symptom indicating a deficiency of which nutrient?
The correct answer is:
Potassium (K):
There are many things which can cause the edge of leaves to become necrotic, but in this case, it is due to a shortage of potassium within the plant.
Results
We hope you enjoyed the quiz and learned something!
See how your score matches up…
1-3: You need to do a few more of these quizzes to become a field diagnostics expert.
3-5: You have made a start in your field diagnostics but there is some way to go…
5-7: You are getting more right than wrong so keep on learning!
7-9: Impressive you are getting pretty experienced in your field diagnostics!
10: Well done! But make sure you do the quiz again next month.
We hope you enjoyed the quiz and learned something!
See how your score matches up…
1-3: You need to do a few more of these quizzes to become a field diagnostics expert.
3-5: You have made a start in your field diagnostics but there is some way to go…
5-7: You are getting more right than wrong so keep on learning!
7-9: Impressive you are getting pretty experienced in your field diagnostics!
10: Well done! But make sure you do the quiz again next month.
