Why does your Zinnia elegans have tiny black flies? Diagnose the cause and fix it with our step-by-step guide.
Pet FriendlyThe tiny black flies are likely adult fungus gnats, whose larvae live in the organic matter of moist soil and feed on decaying roots. In Zinnias, an infestation often follows periods of overwatering or high humidity.
The presence of black flies often indicates that the soil is too wet, which can lead to Pythium or Rhizoctonia. These fungi cause root decay, creating the perfect breeding ground for fungus gnat larvae.
If the flies are hovering around decomposing organic mulch at the base of the Zinnia, they may be fruit flies attracted to fermenting plant matter. While not directly attacking the Zinnia, they indicate a high-moisture environment.
Your plant might also be experiencing one of these issues:
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