Spring is here and for winemakers that means one thing: the inevitable return of our sworn enemy, Drosophila melanogaster, the common fruit fly. Minute little flying monkeys of doom, they’re hard to exclude from your winemaking areas, and while they’re easy to kill, by the time you’ve swatted one, thirteen more have materialized out of thin air, looking for a free meal—females lay 400 eggs each, and they mature in as little as 7 days!
The reason why we need to be concerned over the little monsters isn’t just that they’re unsightly and chewy when you discover one inside a mouthful of Chardonnay. No, it’s their other name we need to think of, ‘Vinegar Fly’. The little blighters are filthy with acetobacteria, the organism that turns our delicious alcohol in to vinegar.
How to combat ‘em? First, understand that they don’t eat fruit: they eat mainly yeast. When they smell carbon dioxide and alcohol, they think it’s a piece of rotting fruit where they can lay eggs and get a delicious meal. When they smell a fermenting carboy, it’s their equivalent of a Vegas buffet ten thousand miles long. You’ll need to wipe up every single little tiny spill of wine or juice immediately, and sulphite the area to prevent any residue from getting a yeast film.
You can set up a wasp trap (available from hardware stores) for them. Make sure to fill it with the magic formula: apple cider vinegar with a couple of drops of liquid dish soap in it. Also, check out natural pyrethrin-based insecticides: they’re made from plant oils, are mostly safe and can be used in food prep areas. Never use any other kind of insecticide around wine or food prep areas! Spray your winemaking area well just before you leave for the day and sweep up the little corpses next morning. (article from Tim Vandergrift, Technical Services Manager, Winexpert Ltd)