Series: Ask Alys  Ask Alys: your gardening questions answered
How can I control the small black flies in the peat-free compost
of my houseplants?     • The Guardian,     • Jump to comments ()
Ask Alys: fungus gnat Unwelcome guest: Fungus gnats love living
in compost high in organic matter. Photograph: Alamy  Since I
started using peat-free compost I've found that the population
of small black flies in the surface of the compost of my
houseplants has exploded. I know they're harmless to the plants,
but a bit irritating in the house. Is there any way of
controlling them? This is a common problem with peat-free
compost, particularly when it's damp, as these flies, known as
fungus gnats, are attracted to compost with a high organic
matter. The maggots of some species can cause damage to
seedlings, but mostly they are simply a nuisance. I cover
the compost of my house plants in a layer of grit or pebbles as
this is a much less appealing home (they inhabit only the
surface layer). I also use yellow sticky traps to