Can it kill fungus gnats? I used the drenching stuff, but when following the directions, it nearly drowned my plants. Next, I set all my plants outdoors for the summer and only took cuttings to root in water. I left the parent plants outdoors to freeze and planted the rooted cuttings in new, good quality potting mix. Alas, the gnats never left home, though they seemed to diminish in number for awhile. I've had houseplants all my adult life, and only in the past five years have these pests taken up residence.