I have several New Guinnea Impatiens, Petunias, and Geraniums in my pots and hangers. Each time I water them I notice these Gnats scurry to the top, fly around to dry off then right back on and then INTO the soil. The problem, THEY EAT THE ROOTS. The plant looks as though it is wilting from no water, lays over and dies. The root balls have been reduced to the size of your finger tip.
I was looked at as though I was high when I was at a local gardening center and asked the pest expert. She smirked and said try this and walked off! B- word! It was some sort of a granual that I sprinkled on the surface. It worked for a day or two.
The same bugs with the same effect infested a big Fig Tree my wife had right next to a Peace Lily that was unharmed. A year ago, they ate the roots to a point where the tree wouldn't stand on it's own. I treated it with the granular poison from the center, heavily last year and what was left this Spring. I didn't notice them anymore until a week ago. Not many. Maybe one or two.
What the hell are these and why do I get them every year? They destroy my plants each time I buy new. I replace the soil, the pots, and have tried several sprays and granular pesticides with no luck.