Fungus Soil Gnats - Knowledgebase Question

Boston, Ma
Question by blkbeautiful
June 27, 2010
What can I get to treat soil gnats that have bombarded my house plants. I have four house plants that I have to replace due to these gnats. I will try to save them in the meantime. What can I buy at home depot that I can spray on the houseplants or put in the soil that will get rid of these gnats? Also, can I do a home fogger to get rid of them and will that kill the plants?

Answer from NGA
June 27, 2010


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 wouldn't use a fogger indoors and I don't think it's necessary to toss your plants to get rid of fungus gnats. I hope this information helps!

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