Why does your Zinnia marylandica have tiny black flies? Diagnose the cause and fix it with our step-by-step guide.
Pet FriendlyThe tiny black flies are likely the adults of fungus gnats, which thrive in the moist organic matter found in Zinnia potting soil. Their larvae feed on decaying organic material and can damage delicate Zinnia root hairs.
Overwatering Zinnia marylandica creates the damp, anaerobic conditions that fungus gnat populations require to breed. This moisture also makes the plant more susceptible to secondary fungal pathogens.
High levels of uncomposted peat or heavily mulched Zinnia beds provide a perfect breeding ground for fly larvae. As this organic matter breaks down, it attracts various small dipterans.
Your plant might also be experiencing one of these issues:
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