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Fruit Flies & Kombucha

Fruit Flies & Kombucha


Making kombucha can be a beautiful endeavor. Once you get past the newness of the operation, a new SCOBY forming on the surface is a beautiful sight. There are a few things, unfortunately, that can ruin that sight. One is mold - it's something we have covered quite a bit. The other is fruit flies.   The number one enemy in the world of unwanted invaders, the fruit fly (Drosophila melanogaster) is everywhere. In every brew space I’ve ever been I’ve seen these little buggers buzzing around. Even in tightly controlled environments like our SCOBY Lab we see them fly up seemingly out of nowhere. Sometimes it seems like they appear out of thin air (I wouldn’t be surprised if this was the case). There are tricks to getting rid of them, but even more important is keeping them out of your brew jar.   What should one use to cover a brew vessel during fermentation? Your kombucha wants to breathe fresh oxygen during fermentation - so sealing your jar with a hard lid is out of the question. Therefore we turn to material that is porous enough to let air in, but not porous enough to allow fruit flies inside. Our material of choice is organic cotton. It has a tight weave, that if correctly secured to the jar, will not allow fruit flies to get inside. Other materials with the same weave will also work well. A paper towel, an old t-shirt, or even a coffee filter will work great.  

One material that is commonly used, but should not be, is cheese cloth. Although it is designed for food production, it is too porous. Even if it is layered multiple times. We get emails all the time from new brewers using cheese cloth that have a family of fruit flies hanging out on their culture. When this happens the brew must be scrapped. It only takes one

Once one fruit fly gets in, it's all over


First, it will quickly lay its eggs which then turn into maggots


After a few days, they will turn into full-grown fruit flies


The process is quick and before you know it, you have a many flies buzzing around your jar

  But don’t be afraid. With a simple piece of cloth and rubber band, you will be safe from these unwanted but familiar pests!

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  • Eric
Comments 2
  • Jennie

    OH, those dreaded fruit flies. I’ve been battling them all summer….luckily none have gotten into my batches, since I keep them covered tightly with a swatch of cotton cloth. However, just trying to get RID of these things is an ongoing battle. I’ve got glasses of Apple Cider Vinegar around the house to catch them with….nothing like explaining to your guests why you have have filled jars of ‘juice’ around your house! ;)

  • janet

    I wanted to make a comment that having a fruit fly infestation isn’t necessarily the end of the line to your precious SCOBY. I have had probably three attacks .The first two times, I tossed it all, used a new SCOBY from the hotel and started over. But the most recent time I had neglected the SCOBY, when I opened it up, there were lots and l lots of dead fruit flies. Horrified because I no longer had any healthy SCOBY in the jar, I pulled out the five pound mother, pulled off the top and the bottom until I was left with an untouched specimen that I washed off with filtered water. After sanitizing the jar and spout, and rinsing the inside with a small amount of the vinegar, I started again using a tiny amount of brewed sugar and tea and gradually increased it, checking on the pH and taste. I can say that it’s okay now.

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