Question
I sure hope you can help me with my gnat problem.

I'm new to houseplants and did a little research before making my selection.  About two months ago I purchased a fiddle-leaf ficus for my home.  

The plant was initially in a 1 g plastic pot and I repotted it in a 4 g pot with a "Moisture Smart" potting mix.  The plant sits in front of a W facing window so it gets lots of afternoon/late afternoon sun.

Initially I over watered the plant so much so that the water draining out pooled in the plastic tray the pot is resting on.  I tried to sop up as much of the water as possible and then let the plant and pot dry out for about a week maybe two.  From that point on,  I have been watering the plant about once a week. After about three weeks, I began to see gnats in the same room as the ficus.  While watering the plant I heard a crackling noise in the soil.  Upon closer inspection I saw tiny gnats crawling on the surface of the soil.  

The leaves have begun to brown on the edges and I have noticed the gnats sitting on the underside of the leaves closest to the soil.  

What can I do to get rid of the gnats and get my plant healthy?

Thanks!

Answer
Hi Isabel,

Unfortunately, your research did not turn up reliable information for you. Newly acquired plants should never be repotted for at least 6 months, if at all. When repotting is appropriate, you should move the plant up one size only. Moving a plant into an unnecessarily large pot means that the excess soil needed to fill the pot absorbs and retains water for too long. That creates a breeding ground for fungus gnat larvae, but even worse will cause the roots to rot and the plant to die. Had you not repotted, you would not be having any problems with your Ficus lyrata.

The "moisture smart" soil that you used is the source of the gnat larvae. In addition, all that soil stays moist for a long time and creates an environment of decaying organic matter that feeds the larvae.

It is a bit late, but you will have to undo the repotting that you did. Take the plant out of the pot and gently remove and discard all of the soil you added under, around and on top of the original rootball. That will probably eliminate all of the gnat larvae. Put the plant back into its original pot or another 1 gal pot that does not require the addition of any soil. Make sure it has drain holes.

Once your plant is back in its proper pot, then water it thoroughly as soon as the surface of the soil feels dry.

The flying gnats are the adults that die of "old age" after a week, so don't worry about them. As long as you eradicate the larvae, you will break the reproductive cycle and solve the problem. Just be careful not to keep the soil constantly wet. The light you described is fine for a healthy Lyrata.

I have written articles on repotting, plant pests and on Ficus lyrata care that I will email for free to you (or anyone else) who emails a request to me at [email protected]. I have also written an indoor plant care book in a PDF format that I can sell you if you contact me at my email address.

Please let me know if any of this is unclear or if you have any additional questions.

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Will Creed, Interior Landscaper
Horticultural Help, NYC

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