The tiny black fly in a pot that stays wet is a fungus gnat. It is separated from a fruit fly by its tie to the soil. The larva is in the mix; a yellow sticky trap catches the adult and does not end that stage.
What a biological option such as BTI does
BTI is a biological option aimed at the larval stage. A sticky trap does not replace it.
How watering changes
The surface is watered less often, enough that it dries without wilting the plant. The mix is changed if it needs to be.
