Yes it is a Carmona. I have seen several care guides for this species, but not one long term healthy tree. Beginners as well as advanced bonsai artists fail. The care seems to be a big mystery.
What is totally sure without doubt is that in temperate regions it cannot be kept in a windowsill right above a heating element in winter. Your placement is the recepie for disaster and the tree will proboably not make it until spring.
I keep a tortoise in the same room, so could place an additional lamp on top of the tortoise table to keep the tree under in winter. This would work off the timer providing 12 hours simulated Daylight Would that suit?
Is someone able to please offer some advice on the black spots?
Should I remove the leaves with black spots and spray with a fungicide?
My other ficus doesn't look anywhere as nice as this bonsai, and would like this to survive. But the black spots dont look healthy.
Extra light and lower temperature may help. But based on this species natural distribution range I strongly believe that high humidity is a key for long term success.
During the winter the tree needs all leaf surface. Keep an eye on it to follow the progress. If it is spreading fast, I would remove the black leafs. If not, they are useful on the tree. I have no experience in using poison to fight healt issues. But what I am sure about is not to treat If you are not perfectly sure about the diagnosis.
In the end it is good If you know that the chanse of survival is very low. If it doesnt make it, it is not your fault. Next time get a locally hardy tree and grow it outdoors. So much easier. Bonsai is about creating, not about keeping suffering trees alive outside their natural conditions. For a good development you need a perfectly healthy tree that is growing good. Even if you make it survive, there will be very little posibilities for development.
Your tree is still in a windowsill right over a heater. That is sure to weaken the tree. Weak trees are more susceptible to pests. Treating the pest without correcting the environment will not help the tree.
I did not ignore your advice, however I dont have any alternative source of light yet due to the festive period. This is currently the best location I can find for the tree, although granted its not ideal.
The bathroom has almost no light, the north facing extension has 3 outside walls and gets rather cold (As well as having other plants I dont want cross contaminated), The other bedroom is north facing and has an even bigger radiator.
Any advice on the infestation would be appreciated.
So far my experimentation with this species is that cooling it down in winter to establish balance between awailable light and temperature is better than increase light artificially. I cannot draw any full conclusions yet, it is just too early. The tree was purshased in August and still quite healthy.
White flies infestations in greenhouses and indoors is fighted with a combination of remowing most suceptible plants, pinching eggs and larvae by hand, neem oil and Encarsia formosa. It is a time consuming struggle. I don't think you have mentioned your location and climate yet. Anyway, in most temperate regions white flies cannot survive outdoors. So if you make it until spring putting the tree outdoors may be a solution.
On your last photo the tree is looking very dry. What is your watering technique and frequency right now?
The extension gets down to around 14 deg c at night, and around 18 during the day. But this varies depending on outside temp.
When I got the bonsai the soil was very wet indeed. Seemed to have been overwatered.
The very top may look slightly dry but sticking my finger just under the surface it is still moist to the touch. I have a moisture meter so could double check.
I water from the top, My other bonsai (Ficus) gets misted daily, watering when required when the soil starts to feel it is drying slightly.
Should the soil just be kept most on this one as well?
I ordered an led plant light, should arrive tomorrow.
Whats your thoughts on location?
We are normally out during the day and tend not to heat an empty house, the small bedroom haas the tortoise heat lanps on during the day so had planned to sit it on top of that with the light. Thats about the most stable room for temp.