AboutDarlene K. Kittle Expertise I have been a Master Gardener for 20 years and I raise around 300 houseplants a year including tropicals, succulents, and cacti.
Experience She is also studying the Japanese art of bonsai with tropical plants and is President of the Fort Wayne, IN Bonsai Club.
Education/Credentials I am not a hortculturist. I am a Purdue University Master Gardener for over 20 years. I have studied plants on a personal level by growing hundreds of plants annually for the last 35 years. I have also studied under several nationally known American Bonsai experts.
Question I normally have excellet results with my houseplants after setting them outside on the balcony for the summer (Canadian weather). I just brought them in and they have small black flies. Tried Safer's insecticidal soap in the soil, with no luck. These flies are hovering around the plants as well as in the soil. Any suggestions? Thank you.
Answer Renee,
They are fungus gnats and are there because your plants have been overwatered &/or the soil has too much peat moss and is holding water too long so the roots don't have a chance to breath carbon dioxide through the soil between waterings so the roots begin to rot just as though they are sitting in a swamp. The rotting roots attract the fungus gnats. Let the plants dry out more between waterings and the gnats will disappear. Next time you repot those plants go to your nearest garden center and buy a bag of perlite and a bag of horticultural charcoal. Mix 2 parts potting soil with 1 part perlite and 1/4 part of horticultural charcoal. That will make the soil more porous and hold more air so the roots will not rot and attract the fungus gnats.
You can also water the plant with rubbing alcohol. It will kill the flies on contact in the soil and will not hurt the roots. Then you have to follow the above instructions to keep the fungus gnats from recurring.
Good luck.
