Fungal infection?

[Deep Sea Diver]

??….

 

[sciguy1872]

In the other forum from long ago, I was wanting to cut off leaves that were not dark green because I figured they were taking nutrients away from healthy leaves--they said they'll darken.
I see that you are an experienced bonsai grower--just wondering what Shibui thought.

 

[Shibui]

Shibui, do you agree that the leaves look good? In the other forum they told me that leaves grow darker green as they mature.

That may depend on the species. Pretty sure leaves on my Ficus open up the same dark green so I would still suspect some nutrient deficiency.
Maybe give it a week or so to see if the others are correct and leaves do change colour as they mature = no problem.

If leaves remain yellow it's more likely a nutrition deficiency.
NEW leaves yellow means a non mobile element deficiency, otherwise the plant would transfer elements from oldest leaves to ensure new leaves are healthy.
Non mobile elements are: Iron, Copper, Sulphur, Manganese and Zinc. Iron. manganese and Zinc usually show as green leaf veins with yellow between veins. Totally yellow leaves is usually Sulphur or Copper deficiency but I've never actually seen those symptoms.
It is possible that your soil may be too alkaline. That can happen when using tap water which is often pH adjusted to above 7 to stop the water dissolving lead from pipe fittings and causing lead poisoning. Alkaline soil prevents the roots taking the nutrients from the soil.
I would check soil pH first. If above 7, use Iron chelates or sulphur to reduce pH temporarily. Long term use an acidifying fertiliser.
If you can't test pH you could try Iron chelates as directed on the packet. Even if I'm wrong, it should not cause any further harm.

 

[sciguy1872]

That may depend on the species. Pretty sure leaves on my Ficus open up the same dark green so I would still suspect some nutrient deficiency.
Maybe give it a week or so to see if the others are correct and leaves do change colour as they mature = no problem.

If leaves remain yellow it's more likely a nutrition deficiency.
NEW leaves yellow means a non mobile element deficiency, otherwise the plant would transfer elements from oldest leaves to ensure new leaves are healthy.
Non mobile elements are: Iron, Copper, Sulphur, Manganese and Zinc. Iron. manganese and Zinc usually show as green leaf veins with yellow between veins. Totally yellow leaves is usually Sulphur or Copper deficiency but I've never actually seen those symptoms.
It is possible that your soil may be too alkaline. That can happen when using tap water which is often pH adjusted to above 7 to stop the water dissolving lead from pipe fittings and causing lead poisoning. Alkaline soil prevents the roots taking the nutrients from the soil.
I would check soil pH first. If above 7, use Iron chelates or sulphur to reduce pH temporarily. Long term use an acidifying fertiliser.
If you can't test pH you could try Iron chelates as directed on the packet. Even if I'm wrong, it should not cause any further harm.

Hi, Shibui. The species is microcarpa. Is there a bottle of special water that is more acidic than tap water, sold for gardening purposes or something?

 

[Shibui]

Is there a bottle of special water that is more acidic than tap water, sold for gardening purposes or something?

I do not know of such a thing.
We have had growers proposing to make acid water by adding vinegar or other acids but, not knowing how much to add per litre means flirting with more problems IMHO because too acid can be just as bad as too alkaline. It's up to you if you would like to try home made recipes.
There are several acid fertilisers available that can help - I think Miracid is one that's commonly available in the US. I think another brand was mentioned somewhere too.
You don't have a location in your profile so may or may not be able to get that brand in your area.

 

[EHA]

Remember irrigation water pH is just part of the puzzle. You have to do soil pH tests before embarking on trying to change irrigation water pH. If you know your area has high alkalinity water then yes, pH adjustment could be necessary. Remember plants are able to pump out hydrogen ions directly around the root hairs to change the pH of the water surrounding the root hairs to a certain degree. Obviously if the pH of the soil is so high the plant wont be able to compensate. Usually fertilisers for acid loving plants contain urea and ammonia and need bacterial breakdown to acidify the soil by liberating hydrogen ions. This is a slow process, so do not expect immediate results.