Set by Dr Eric Boa
Let’s go back to basics for the next few months. It will allow Phil Taylor, the regular setter, to replenish his photo library of symptoms and causes and have a well-earned pause. Going back to basics means that there are only three possible answers; and they’re the same for each photo. Welcome to the ABC method: abiotic, biotic or confused.
You have to decide whether the symptoms represent or indicate pest or pathogen attack (Biotic) or are the result of something which is not a living organism (Abiotic), such as damage due to lack of water, nutrient imbalance, wind, chemicals and so on. If you can’t decide, there’s a third option: confused. Regular quizzers will appreciate that it’s often far from easy to distinguish what is and isn’t a disease or pest attack.
I’ve found this method useful in getting to grips with symptoms on all plants. ABC is the start of a process to narrow down the causes and particularly helpful with plants you don’t know well. ‘Confused’ should be a conscious choice. It’s better to be honest than have doubts about possible abiotic or biotic causes. If you recognize any of the ‘confused’ examples then let me know!
#1. A common feature on garlic, onions and leeks.
The correct answer is:
Comments:
These are the pustules of a rust (Puccinia porrii). Look out for it on wild garlic, now flowering profusely
#2. Why are these potato shoots dead? Perhaps it’s a disease, or maybe not …
The correct answer is:
Comments:
A severe frost damaged these tender potato shoots. Note that all died suddenly at the same time, suggesting a massive change. In this case, it’s unseasonably cold temperatures overnight (in Bolivia).
#3. Late season rhubarb from a trial plot at Wisley (Royal Horticultural Society) in the UK. What is the general category of cause?
#4. Badly distorted peach leaves. What is the general category or type of cause?
#5. A rowan tree in steep decline. Note the damage to the trunk. Is this physical damage or some type of pest or pathogen (i.e. biotic)?
The correct answer is:
Comments:
Time for a confession: this was in my parents’ garden and I was ‘confused’ for many years until a chance comment by a colleague: rowan is a host for fireblight, a bacterial disease. Perhaps more often seen on hawthorn in natural settings and of course a big problem on apple and other fruit trees in the Rose family.
#6. Pot-grown tomato declines and dies in a couple of weeks.
#7. Dead and drying leaves in the lower foliage of an avocado tree.
The correct answer is:
Comments:
Fire damage, probably because the farmer has burnt the understorey crop in preparation for a new sowing.
#8. Roots of poorly growing radish.
The correct answer is:
Comments:
Unusual growth and swellings on a root suggest either nematodes – or in this case clubroot.
#9. Detached pods of broad beans, showing a range of symptoms.
#10. A punnet of strawberries with many unsuitable for sale.
The correct answer is:
Comments:
This could just be a tray of squashed and rotting strawberries, but note the grey mould on several fruits. Botrytis is a big problem for commercial growers.
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.
