Some people use sticky yellow paper to catch mature fungus gnats.
I would rather make the soil surface unattractive by keeping it dry - add coarse bark shreds on top of the soilless mix.
Maybe bottom-water most of the time. Flush the pot sometimes.
And keep organic stuff out of the pots. Few organics => little or no fungus => no fungus gnats.
I'm kind of hoping the little balls are baby mushrooms from mushroom compost in the mix.
That would also explain fungus gnats.
We should ask:
Are the balls hard like Perlite or squishy?
Do they smell different from the soilless mix in the tree-pot, or the other pot?
Are they still growing rapidly? At all?
If you spoon a few into water, do they dissolve?
