Hi everyone, newbie to this forum! I'm hoping someone can help me.
I've owned a Fukien tea for about a year. 6 months ago I noticed a small colony of scale insects, so resorted to alcohol and cotton buds to pick them off one by one, followed by a mild neem oil spray (homemade). It didn't affect the plant. Then 3 months ago, I noticed the scale insects were back. This time I covered the leaves top and bottom in my homemade spray. Needless to say, the Fukien did not like this at all and decided to dropped half of all its leaves a week later, in the space of one night.

I started researching about Fukiens a little more and realised it would thrive in my bathroom where I previously grew a pineapple (here in London)!! Anyway, the bathroom is very bright, warm and humid (excess controlled with a dehumidifier). The Fukien has grown really well since, sprouting long shoots which I've had to cut back to ensure the lower parts of the tree would regrow the leaves it had dropped. So happy story so far.

Yesterday, I discovered that whilst leaves are beautifully green on the top, some of them have turned completely black underneath. Not a spot, but fully covered in black (except for the veins). I've never seen this condition before. The black does not scrape off, it almost looks like it's meant to be that way. Anyway, as a precaution, I sprayed it with anti fungus, but was hoping to get advice from here as soon as possible before the Fukien sulks again and drops half its leaves.

I've attached photos of the issue. I've marked with a blue spot the same leaf, so you get an idea of how green the top is vs. the underside of the leaf!

Any help would be much appreciated.

Did you research:

1-) Black Spot disease;
2-) Anthracnose, a group of fungal diseases that affect a variety of plants in warm, humid areas.

A very humid environment such as your bathroom, with little air circulation, can cause fungus to thrive.
Please read below:

"Symptoms of leaf spots vary depending upon the causal agent. Although leaf spots can be caused by air pollutants, insects and bacteria et al., most are a result of infection by pathogenic fungi. Once into the leaf, the fungi continue to grow and leaf tissue is destroyed. Resulting spots vary in size from that of a pinhead to spots that encompass the entire leaf. Dead areas on the leaves are usually brown, black, tan or reddish in color. Occasionally the necrotic areas have a red or purple border. Partial to complete defoliation may occur under favorable conditions for the causal fungus."

I am NOT saying your plant has any of these diseases (the cause could be simpler), but I would investigate.

Many thanks Clicio.

I conducted further research after posting, I believe it must be black spot disease. The anti fungal spray I applied that evening seems to be helping. My bathroom isn't excessively humid (I keep it at 50% - the setting I leave my dehumidifier on) and there is good air circulation as I leave the skylight open all day (I close it at night to avoid the plants getting cold here in London). Luckily none of my orchids, pineapple plant, or aloe vera (which are all thriving in this bathroom) have any issues.

I'll keep you posted to confirm whether the anti fungal spray worked.

All the best!

Cawauk wrote:

I conducted further research after posting, I believe it must be black spot disease.

Great news about the research and the probable culprit; now you can have a fight against it!

Cawauk wrote:

I'll keep you posted to confirm whether the anti fungal spray worked.

Please do so.