bacbbe5f_elphia_County_Master_Gardeners__How_to_DIY
[Management Method] Apple Cider Vinegar Trap [Who/What it Manages] Fruit flies, fungus gnats [How to DIY] 
In a small container (I use a half-pint jar) fill with apple cider vinegar, cover tightly with plastic wrap and secure (I screw the jar rim over the plastic wrap but you can use rubber bands or tape) Poke small holes in top of plastic wrap and place near the most insect activity. Insects get in but can’t get out. Replace every 2 weeks, every 1 week in humid summer weather.
Philadelphia County Master Gardeners
How to DIY