How long can the eggs/larvae/pupae of indoor plant bugs survive in soil that is not being watered at all? For example, after the plants have died and been removed, so literally no water at all is being added to the pot.

I have some medium-sized pots of soil that have been sitting dry inside for 8 months, and some other small pots of soil that have been sitting dry for 3 weeks. Are bugs likely to still be alive in either of these situations?

Specifically, fungus gnats and thrips.


  • Are you sure they're fungus gnats? I ask since some things that sort of resemble fungus gnats can live much longer. Commented May 19, 2021 at 7:59

1 Answer 1


Fungus gnat eggs cannot survive in dry soil for more than 1 or 2 days but thrips can hibernate in the soil as eggs for an entire winter season and the adults can live up to 45 days. If the soil was infested I recommend either discarding the soil outside or sterilizing the soil before using it again.

To sterilize potting soil place in a oven safe tray and set your oven to 200°F. If you have a thermometer you want the soil to reach a temp of at least 160°F for at least 30 minutes to kill bugs but if you don't have one, baking for 45-50 minutes will work. Don't go much over 200°F or you can burn the soil.

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