Why does your Bunching Onion Estafette F1 have tiny black flies? Diagnose the cause and fix it with our step-by-step guide.
The tiny black flies are likely fungus gnats, whose larvae live in the moist organic matter of the onion substrate. They thrive in the high-moisture environments often required for Allium germination and can feed on delicate developing roots.
While Black Scab is a fungal pathogen, the presence of decaying organic matter or weakened onion tissue caused by fungi can attract various small dipterans. If the onions show dark lesions alongside the flies, a fungal issue may be the primary driver.
Excessive moisture in the potting medium promotes the growth of fungi and bacteria, creating a perfect breeding ground for soil-dwelling flies. Bunching onions are sensitive to anaerobic soil conditions which accelerate this cycle.
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