My soil is infested with large black flies. They stick to the walls of my house and love resting on the soil. Every time I plant something, more come. How can I get rid out them? Is there anything I can put in my soil?
Cluster Flies are what you are dealing with. In the spring the female flies lay their eggs in the soil and then adult flies eventually come to the surface and continue the cycle.
You can try adding beneficial nematodes to the soil.
Here are some links with more information.