Hey there! I’m relatively new to bonsai care, and my partner has gifted me a Fukien Tea tree a while ago, but our tree has gotten aphids and the leaves are now turning brown/black with patches. I have attached photos for an example. I’ve done extensive reading on forums for how to care for my Fukien Tea. However, this does not make me an expert and I would really appreciate help here! I’ve used a neem oil spray as a pesticide treatment, could my plant be reacting to that? Or is there a bigger issue going on?

It is the aphids not neem oil causing the problem, if you used it correctly. There are no pictures, but if there are aphids they will d a lot of damage. It is better to water the neem oil into the soil as it is systemic and will work for longer, however it does not work instantly, it takes at least 7 to 10 days to start to become effective. Make sure that you are watering correctly and the plant is getting plenty of sunlight

Hey there! I thought my attachment went through. Hope these help and thank you for your attention!

And another one.

Aphids are the cause,