Why does your Nephrolepis exaltata (Boston Fern) have tiny black flies? Diagnose the cause and fix it with our step-by-step guide.
Pet FriendlyThe tiny black flies are likely the adult stage of fungus gnats, which thrive in the moist, organic-rich substrate preferred by Boston Ferns. Their larvae live in the top layer of soil and feed on decaying organic matter and occasionally fine root hairs.
Boston Ferns require high humidity, but overly saturated soil creates an ideal breeding ground for fungus gnat larvae. Constant wetness prevents the top layer of substrate from drying out, allowing fly populations to explode.
Frequent application of organic liquid fertilizers or compost tea can introduce larvae or provide a nutrient-rich environment that attracts flies. High nitrogen levels in the substrate can stimulate fungal growth, which is the primary food source for gnat larvae.
Your plant might also be experiencing one of these issues:
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