Getting rid of gnats in your bonsai soil

Gnats can be a common problem in plants kept indoors including bonsai. If you notice little flying bugs around your indoor plants and trees you probably have fungus gnats. Their young feed off the fungus in the soil. Hence the name, fungus gnats. They are a problem indoors because there are a lack of natural predators to control them and soil conditions indoors are more favorable for them.

Are fungus gnats harmful to my bonsai tree?

The gnats themselves are not very harmful to established plants or bonsai, but the conditions that are favorable for them are. The presence of these bugs usually means you are overwatering your indoor bonsai or houseplant. Keeping the soil too damp is not good for the roots of your tree. The second problem is that they can feed off young roots which is especially harmful to young plants. As a bonsai's roots are very important one should be vigilent against gnats.

Getting rid of fungus gnats

Getting rid of the gnats is fairly easy. First, stop overwatering your plants. Let the soil dry out more. The gnat larvae live in the upper part of the soil bed. If you let that part dry out the fungus they eat will be reduced and so will the gnats. If you are using a well draining bonsai medium the problem should go away fairly quickly. If that doesn't stop the gnats you can add in some insect sticky pads or fly tape and as a further measure you can treat the soil with insectides labeled for gnat control, but this should be a last resort. Additionally, insecticidal soap does not work very well on treating gnats in the soil.

Solutions in order of least to most aggressive
  1. Stop overwatering
  2. Capture existing with sticky pads
  3. Treat soil with a systemic
  4. Repot your bonsai with a better draining soil

Homemade DIY fungus gnat trap

Items needed
  1. Glass Jar
  2. 5 tablespoons apple cider or white vinegar
  3. Rubber band

Place the vinegar in the jar and then cover the jar with the plastic wrap. Secure the plastic wrap with the rubber band. After, poke some very small holes in the plastic wrap. The gnats will be attracted to the vinegar, but will be unable to escape the jar.

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