Why does your Bunching Onion Tycoon 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 organic matter of the soil and feed on decaying roots. In bunching onions, high soil moisture levels often trigger outbreaks as they thrive in damp environments needed for onion development.
While the visible flies are adults, they may be attracted to a substrate already suffering from root maggot infestations. These larvae tunnel into the bulbous base of Tycoon onions, causing structural weakness and potential rot.
While not a direct cause of flies, overwatering creates the perfect breeding ground for fungus gnats. For Tycoon bunching onions, constant wetness can also lead to secondary bacterial soft rot, which produces odors that attract various small dipterans.
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