Black Spots on Azalea

[Adamantium]

Hey all, is this something to worry about? It's a new to me azalea coming from Louisiana. It's got a great trunk, so I hope it's not something that's fatal. It's not on the whole tree, just about 1/4 of it.

 

[Stan Kengai]

Looks like leaf spot typically caused by fungus, probably from being watered from overhead. It's not serious, but can spread to other plants. Treat with appropriate fungicide. Do not water the leaves. When leaves fall, clean them up and dispose of them.

 

[GrimLore]

This season I had three plants otherwise healthy doing the same early in the new growth stages. They were bougainvillea, African sumac, and strawberry guava which I separated from all other plants. That looks post bloom so it should be throwing new growth at this time which is light green as were the plants I referenced.

It was rather puzzling and there was no visible sign of infestation and no good reason to blame it on fungal.

I took a long shot and decided it was parasitic. I wrapped the pots with saran wrap and trimmed all the nasty looking foliage off. I then sprayed the underside of every leaf and cut with Neem Oil(not the top of the leaf) although a small amount of drip gently wiped off did no harm. After unwrapping I treated the soil surface with a few shots of malathion(again, flying blind)

They are now all growing new foliage that looks proper and have been for a few weeks since the single treatment...

No, clue what it was, and was tired of advice on fungal, etc... because for the most part had little good results.

Grimmy

 

[Adamantium]

Looks like leaf spot typically caused by fungus, probably from being watered from overhead. It's not serious, but can spread to other plants. Treat with appropriate fungicide. Do not water the leaves. When leaves fall, clean them up and dispose of them.

Would Daconil cut it?

 

[Stan Kengai]

Would Daconil cut it?

Daconil or liquid copper are standard treatments. Copper is milder. It does not kill the fungus, but prevents it from reproducing. Daconil is more like an atomic bomb.

 

[Adamantium]

Daconil or liquid copper are standard treatments. Copper is milder. It does not kill the fungus, but prevents it from reproducing. Daconil is more like an atomic bomb.

Well, I already have Daconil, so Daconil it is haha

Glad it’s nothing that should be fatal.

 

[GrimLore]

Well, I already have Daconil, so Daconil it is haha

I used it on Azalea once weekly for a few months to get rid of/control rust. Yours has pubescent leaf so I would still just spray the undersides of the leaf and the branch structure as you see fit.

Grimmy

 

[Adamantium]

I used it on Azalea once weekly for a few months to get rid of/control rust. Yours has pubescent leaf so I would still just spray the undersides of the leaf and the branch structure as you see fit.

Grimmy

Thanks, Grimmy! Why only the underside, if I may ask?

 

[GrimLore]

Thanks, Grimmy! Why only the underside, if I may ask?

The pictures indicate it has pubescent leaf where they are healthy. On plants that have that type of leaf it is to help a couple of different ways with transpiration. I don't spray or treat the fuzzy top leaf for that reason as I want to encourage healthy growth to stay healthy. I remove affected foliage which will not get healthy anyways and treat...

Grimmy

 

[Adamantium]

The pictures indicate it has pubescent leaf where they are healthy. On plants that have that type of leaf it is to help a couple of different ways with transpiration. I don't spray or treat the fuzzy top leaf for that reason as I want to encourage healthy growth to stay healthy. I remove affected foliage which will not get healthy anyways and treat...

Grimmy

So spraying the top would hinder transpiration?

I thought stomata were on the underside of leaves in most species?

 

[GrimLore]

So spraying the top would hinder transpiration?

I thought stomata were on the underside of leaves in most species?

Your pictures indicate otherwise, for the record I have had several types of Azalea that are much the same. The same rules do not apply for all plants and once again, don't treat what is healthy

Grimmy

 

[Adamantium]

Your pictures indicate otherwise, for the record I have had several types of Azalea that are much the same. The same rules do not apply for all plants and once again, don't treat what is healthy

Grimmy

I’m sorry, I’m not sure I follow. My pictures indicate what?

 

[GrimLore]

The first picture, all of the tops of the healthy foliage on the left show pubescent leaf - the fuzz/fiber/hair like stuff. That is not stomata

Grimmy

 

[Adamantium]

The first picture, all of the tops of the healthy foliage on the left show pubescent leaf - the fuzz/fiber/hair like stuff. That is not stomata

Grimmy

Right. Totally understood. That’s why I’m confused. You advise to spray the undersides with daconil to avoid inhibiting transpiration, but stomata are on the undersides of leaves (typically).

 

[GrimLore]

Right. Totally understood. That’s why I’m confused. You advise to spray the undersides with daconil to avoid inhibiting transpiration, but stomata are on the undersides of leaves (typically).

I advised to use the Neem oil on the undersides as I am still pretty certain it is parasitic for a few reasons. Daconil is for fungal, and yes the bad foliage should be removed and the branch structure that is related should be treated if you think that is what needed. Getting some on areas close by will most likely not bother the healthy leaf much but would be pretty hard to avoid.
I see the confusion in that post #3 is not fungal related. The fiber like pubescent leaf that is not affected simply does not need Daconil if that's what you decide and yes they do also aid transpiration.

Grimmy