Why does your Hosta undulata Albo-marginata have tiny black flies? Diagnose the cause and fix it with our step-by-step guide.
The tiny black flies are likely the adult stage of fungus gnats, which breed in the moist organic matter of Hosta soil. Their larvae feed on decaying plant material and fine root hairs, potentially damaging the hosta's nutrient uptake.
Hosta undulata prefers moist but well-drained soil; constant saturation creates an ideal breeding ground for moisture-loving insects like fungus gnats. Excessively wet soil also increases the risk of fungal pathogens attacking the hosta's rhizomes.
Old, decomposing Hosta leaves or excessive mulch around the base of the plant provide a perfect food source and habitat for insect larvae. This accumulation of organic debris can also harbor various soil-borne pathogens.
Your plant might also be experiencing one of these issues:
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