desert rose has fungus gnats?

Pittsburgh, PA

I think my desert rose may have fungus gnats. They look like fruit flies and stay close to the soil - they become quite noticable when I water my desert rose and occasionally they are flying around the house. A few of my other houseplants have had these same gnats in the past - they seem to go away in the winter. Also the soil at the top of the plant has a rusty look to it. My plant seems healthy but isn't growing at all. I was thinking of removing the top few inches of soil and replacing it with a new well draining soil but I don't know what soil I should use. Any advice would be appreciated.

Dublin, CA(Zone 9a)

Typically when there are fungus gnats around it means the soil is staying too moist. In the case of the desert rose which is a succulent, I expect the excess water is going to be worse for it in the long run than the gnats so I would definitely correct your watering. If the soil doesn't drain well enough, you're going to need to replace all of it not just the top couple inches, but it could be if you just back off on your watering it'll be fine unless you know the potting mix you put it in was poor quality to begin with. As far as the gnats, you can use yellow sticky traps to catch the adults (which don't hurt plants, but do lay eggs), and the next time the plant needs to be watered, get some Bt (Bacillus thuringiensis, same stuff that's in mosquito dunks) and water with that, it should help with the larvae in the soil. Some people find that putting a layer of rocks/gravel across the top of the soil helps prevent them so you might try that to keep them from coming back.

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