QUIZ: Leaf Ailments - 8 photos

[beccahoo]

Thank you to everyone in advance who participate in this quiz to help us newbies learn how to identify ailments on our leaves!!

[Tindomul]

I want to learn too, so I am subscribing.

[beccahoo]

Yes hopefully we can get more people to help!!

[Selmo]

Being that these photo are of leaves only, there are usually only a few choices, leaf spots or viruses. But, here goes (these are just my guesses, fore I'm not an expert and would need more information to make better guesses)
A. One of the leaf spots, guignardia
B. Cymbidium virus
C. One of the leaf spots, phyllosticta
D. Sun burn and erwinia maybe
E and F. Looks like one of the leaf spots
G. Erwinia or pseudomonas
H. Anthracnose
Once agian, these are only guesses. These pathogens can look different on different types of orchids. The link at the top of the page is a good place to start. And will give you better information on how to treat these pathogens. Hope this is a start and others can chime in that are more knowledgable than I. Would like to know if I passed the quiz.

[Tindomul]

H looks like something I see a lot in my collections.

[beccahoo]

Selmo thank you for you reply!! I did some homework for you. Perhaps it can help ?

photo uploading

[Ray]

This is a nice idea, but diseases are awfully difficult to diagnose by visual inspection alone, as many look quite similar. Not to mention that what looks like a disease might be a response to some cultural issue.

One misdiagnosis, for example, is attributing dead, black tips on new growths to a fungal infection, when in fact it is due to a deficiency in calcium. Sure, fungi can grow on necrotic tissue, but a fungicide won't fix it.

[estación seca]

Originally Posted by Ray

This is a nice idea, but diseases are awfully difficult to diagnose by visual inspection alone, as many look quite similar. Not to mention that what looks like a disease might be a response to some cultural issue.

One misdiagnosis, for example, is attributing dead, black tips on new growths to a fungal infection, when in fact it is due to a deficiency in calcium. Sure, fungi can grow on necrotic tissue, but a fungicide won't fix it.

I suspect a lot of people attribute black areas to calcium deficiency when they are actually fungal infection.

[charlesf6]

okay where's the answers?

[Gage]

D. There are 2 issues here. One is most certainly sunburn, indicated by the gray haze on both leaves and the large black area on the lower leaf. The second is the tiny black speckles that appear to have been present prior to the sunburn, which could be from any number of things including insect damage or fungus.
F. This looks like mite damage. If the mites are still present, you can wipe a white cloth or paper towel underneath the leaf and see them on the cloth as a orange or brown smear.