Question
I have a Meyer Lemon Tree (2' + tall) that I purchased a few weeks ago from my local Lowes hardware store. I live in Seattle Washington and this tree will be a permanent indoor plant.  It is doing really well in my southern window after the transplant into its new pot (so far, no leaf loss and new flowers and lots tiny lemons have appeared since bringing it home), but I fear I now have a Fungus Gnat infestation.

The "flies" are small, black and clumsy. They stay within the vicinity of the plant base and canopy. I am kind of obsessing over this tree and I have done a ton of research to try and find a way to rid it of them without using pesticides. Over the last week I have tried the bowl of soapy water trick. I put two small bowls of soapy water with a little yellow food coloring in them right in on top of the pot and I am catching a bunch of the little buggers every day. But my goal is to eliminate them.  I have read that I can use 1 part hydrogen peroxide to 4 parts water to kill the larva on contact and stop the cycle. But I am terrified that I will damage the tree! I don抰 want to risk doing any harm to it. Or should I just keep soldiering on with my little bowls of soapy yellow water until I have out-lived the life cycle of the very last one and make sure that I let the soil pretty much dry out before watering it again? I was also wondering it is true that the gnats possibly came the potting soil I used to repot the plant?

Thank you so much for your time!

Answer
Hi Jessica:
Sorry for the delay. I was visiting w/my next door neighbor to my office.  He is a "bug" person- I am not!! Here is his suggestion.  ORTHO Home Defense Max.  It contains 0.05% Bifenthrin insecticide.  It is a ready to use product that needs to be sprayed directly on the surface of the soil in the pot- no need to disturb soil afterwards. It can be used inside and outside.  I am not aware of it causing any injury to leaves and stems of plants if the spray gets on these parts.  You can test a couple of leaves with a spray of the stuff.  Be sure to read the label information before applying.

I need to use this product too!  I have a potted philodendron in my office that these small black gnats have come from the soil and fly around in my office.  I am almost positive they came in the bagged potting soil that I bought a while back. The larvae of these fungus gnats are reported to feed on the roots of plants. To me they are more of a big nuisance.

Steve