Black soots on plants leaves

Question

The black soot is more on plants under palms and coconut trees.

Answer 1

It sounds like sooty mold, which is a symptom of several kinds of pests. I recommend treating the plants with neem oil. This will kill any pests on the plant and treat the sooty mold as well. Here is more information:
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm