Do you use the recommended dosage on the bottle for foliar spray? I believe it's 1:5.
I mix 1 tablespoon sm-90, 1 teaspoon neem oil, and 1 teaspoon karanja oil with 1.5 liters of water as a foliar spray for spider mites. I usually see 1 or 2 fungus gnats flying around, but then again I don't...