I had to leave for a couple of weeks and left my bonsai (a ficus benjamina) in the hands of a friend. Upon my return I noticed that the beautiful white mold on the earth that is beginning to expand also on the aerial roots had appeared, evidently causing too much watering.
What can I do to eradicate it without causing bonsai problems?
Thanks for your attention
first of all put your bonsai in a well-ventilated place and stop watering completely; if possible try to remove the mold and the soil it sinks into. If it were possible it would be better to even repot the bonsai. Remove it from the jar and wash the container thoroughly, leaving it to dry in the sun; the roots will be dusted with a generic fungicide; then the bonsai will be repotted with fresh soil, and of good quality.
After doing all of this maybe we need to thank his friend with a beer, taking advantage of the evening to explain to him how to water a ficus bonsai in winter, so that this incident does not happen again.