The first step in eliminating fruit flies from your kombucha is to make sure your fermentation vessel is tightly covered with a rubber band or brewer’s cap. If you leave it uncovered, fruit flies can easily enter the fermentation vessel. Also, be sure to avoid leaving your fermentation vessel uncovered for long periods of time. Another important step in preventing fruit flies is to use a cover that is not too porous, such as a cheesecloth or other small-woven cloth.
When you are cleaning your brew container, make sure that you don’t use dish soap or any other cleaning products. You can also use a funnel to catch fruit flies that are attracted to kombucha. Once inside, fruit flies won’t be able to escape, and they’ll drown.
To treat fruit flies, you can use one of two types of insecticides. The first one is called pyrethrin, which is safe for use on wine making areas. The second type is called synthetic pyrethroid, which is more persistent and toxic for people and pets. It’s particularly harmful to children and cats, since they lack the enzyme necessary to break it down.
Another way to avoid fruit flies is to make your brew cooler. If your fermentation brew is still too hot, you can put some apple cider vinegar to prevent fruit flies from settling on top of your fermented kombucha. The vinegar will attract the fruit flies, which will then sink to the bottom of the jar. If this doesn’t work, you can use liquid dish soap.