Gnats and organic matter are a match made in evolution. I could have controlled the gnats better. Eventually they'll go away. I'm serious about my tolerance for other earthlings, gnats included.
The application of a pesticide is the act of admitting your crop has failed---paraphrased from Dr's Albrecht, Reams and others.
It works like this: sugar can't be digested by insects. When they get too much of it, it turns to alcohol which will kill the insect. Insects know this, which is why they target low brix plants. Low brix=low nutritional value for humans...but good food for bugs.
High Brix plants have different UV light patterns and different electrical charges which communicate to insects to STAY AWAY...deadly for them.
Them are just facts. The reason those of us growing HB don't have much if any insect pressure is because of the soil. This isn't my opinion. It's not just my experience, either. Everyone notices this when they have properly designed soil.