Gnats around my houseplants - Knowledgebase Question

Las Vegas, Ne
Question by rvegasyo
May 8, 2009
I love houseplants but every year around this time I get these little black flying insects (I was told they are gnats) flying around them, it starts off with a couple but turns into what appears to be hundreds, I finally have to remove my houseplants to get rid of them. I'd like to keep my houseplants, any suggestions?

Answer from NGA
May 8, 2009


Here are two strategies for controlling fungus gnats. They breed in moist potting soil, so you can break the breeding cycle by allowing the surface of the soil to dry out. If you have plants that need moist soil simply place a quick draining and fast drying layer of gravel or sand on top of the potting soil. This will act as a barrier to the soil. Or, you can drape plastic wrap over the soil (cut a slit so you can place it close to the stems of your plant, then overlap the cut ends so the pests cannot find a way to the potting soil). You have to be a little patient with this method because you have to wait through the next generation's maturation before they are gone for good. In other words, once the generation now already in the soil become adults and die off without being able to reproduce, there should be no more gnats. Another method is to use a product called Gnatrol as a soil drench, another is to use an insecticidal soap as a soil drench. Of course, always follow the label instructions carefully. I hope this helps!

Name: Lin
Florida Zone 9b, 10a

Answer from plantladylin
August 31, 2017


Fungus Gnats are usually present due to high moisture levels in the soil. The adult gnats we see flying around our houseplants have a very short life span and can be trapped and killed by placing yellow sticky tape near the plant or by placing the entire plant into a basin or bucket and spraying with an insecticidal soap spray, which will kill the flying gnats.

The gnat larvae beneath the soil thrives on moisture and feeds on the organic matter in the soil; causing damage to the plant by chewing on the roots. To eradicate the larvae and stop the recurrence of fungal gnats, always allow the top inch or two of the soil to dry out before watering.

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