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Sterilizing small amount of Potting Mix

Posted by ottawan_z5a (My Page) on
Thu, Mar 19, 09 at 0:47

Can I sterilize small amounts of commercial potting mix (such as Schultz Potting Soil) to be used in 18 oz container by using a microwave cooker to kill anything (eggs, larvae etc) that may infest the commercial soil mix. Most of the time such soil mixes are supposed to be sterilized but then you get fungus gnats out of nowhere and the only suspect could be the potting mix and not the seeds or sterilized cuttings. My plant containers are isolated in a clear plastic storage box and get fungus gnats and would like to eliminate the probability of soil as the carrier. I know there are chemical solution available to kill the fungus gnats larvae but I want to try to sterilize the soil first and see if it will help.

Follow-Up Postings:

RE: Sterilizing small amount of Potting Mix

Try baking it. I had a springtail problem for a while, and it was one of the solutions that popped up in a search. It was posted across many pet turtle-related forums.

I didn't try it personally, because the problem solved when I solved the other problem my few infected pots had.

Here is a link that might be useful:

RE: Sterilizing small amount of Potting Mix

Baking any soil, or microwaving, will cause a stench in your house that will be difficult to get rid of. Pouring boiling water over your mix would be better, if done outside.

RE: Sterilizing small amount of Potting Mix

  • Posted by jean001 z8aPortland, OR (My Page) on
    Thu, Mar 19, 09 at 22:26

And that stench means it was over-heated and has released materials that are potentially toxic to your plants.

RE: Sterilizing small amount of Potting Mix

I had a nearly full bag of seed starting mix left over from last year. It had been in my garage (half-open) ever since. I didn't want to waste it, so I put it in the freezer for a few days. I used it to start some seeds after Valentine's day and so far, not a single seedling has dampened-off. No fungus knats, either.

RE: Sterilizing small amount of Potting Mix

I put soil in bags and let them sit in the back of the car for a couple of weeks in hot weather. It helps reduce weeds, probably also some pathogens.

RE: Sterilizing small amount of Potting Mix

Tap water should be hot enough if you rinse it thoroughly after hot water has reached the faucet. I'd just leave the bag wide open in the sun for a few days until it is completely dry. Fungus gnat larvae can't survive in dry soil. You could also spread it out on cardboard to let it dry. Of course with weather like we're having that would be impossible here right now.

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