Build a Fruit Fly Trap

Almost every home winemaker has discovered that besides fermenting grapes, they've taken on an unintended hobby of farming fruit flies. I've certainly noticed that through several years of wine making. Though their life span is only about 30 days, it seems that the breeding habits of fruit flies put means that they are almost always likely to be around the house when you have are most active with your foods - whether canning or wine making. For wine making, enough fruit flies buzzing in your primary fermentation tank at low alcohol levels will yield vinegar rather than wine. There's nothing like Napa-grade vinegar when you were counting on Cabernet!

In the attached picture, you can see my little fruit fly "spa". This jar has an inverted paper funnel taped to it. In the jar is an ounce or so of "special sauce" that seems to draw fruit flies right in, away from my fermenting pails and carboys. The sauce is a blend of about equal parts wine, vinegar, grape juice (or a mashed grape) and liquid soap or dishwashing liquid. You only need a touch of each, enough to cover the bottom of your jar.

Fruit flies will find their way into the jar, through the funnel, and drown in the sauce. Over time, your sauce will dry out. Just add a bit more wine or grape juice to the mix when that happens. At the end of the fruit fly season, discard the jar; or remove funnel and clean.

A couple of things to keep in mind in building the trap:

The funnel should reach well into the jar, but not touch the liquid. You want the flies to crawl down the funnel and into the air space around the funnel. The sauce is at the bottom to both attract them, and to cause them to drown. (The dishwashing liquid is part of the mix because it removes surface tension from the liquid, making it impossible for the fruit flies to simply stand on top of it.)

When you place the funnel into the jar, be sure to fully tape around the sides of the glass where the funnel touches it. If you don't the fruit flies will crawl up the sides of the glass and wriggle out around the funnel and the glass. You need to keep them inside the glass.

The fruit fly trap can be kept near food during fruit fly season; it will not smell bad. (The smell is simply one of fermenting fruit, which is what is attracting the fruit flies in the first place.)