If you have ants and flies around your ficus, there are probably aphids feeding on the leaves and excreting a sticky substance called honeydew. Ants love this and will protect the aphids in order to keep a constant supply. Treat to eliminate the aphids and the ants and flies will leave as well. Insecticidal soap works great. Be sure to coat the undersides of the leaves, the stems, and the upper sides of the leaves.
Best wishes with your ficus!
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