Answer: If they are white, they are whiteflies; if they are black they are probably fungus gnats. Whiteflies are difficult to control because they fly so quickly, but insecticidal soap, if it contacts them, will kill the pests. The best approach is to spray in the early morning or at dusk when the whiteflies are resting. Fungus gnats feed and breed in decaying organic matter such as mulch or plant debris. Raking away debris and mulch will expose the soil to fresh air and sunshine which will help it dry out. Best wishes with your landscape.
Q&A Library Searching Tips