Ah, fungus.
Alright, you're in luck (kinda) as it's white and fluffy it's not a fast runner that's going to spread across the entire surface and attack the rest of the seedlings.
With a clean spoon, I'd dig in and remove the dead sprouts. That's the fungus's food source that we want to deprive it of.
IF you can determine that there's a mycological matt that's formed under the soil surface, things might get a little more complicated.
But this seems like it's localized.
Look for matting across the surface of your soil medium after the removal of the affected/dead sprouts.
Depending on the development of your seedlings an if they've developed real roots or they're still "fuzzy" at their base.
IF they're still young and "white fuzzy" you can't try out the tub with air exposure.
That's one of the first and easiest things to do with a surface fungus that's living due to the high humidity, is to dry it out.
IF the fungus is diving down into the soil (based on your spoon removal of the substrate) then the drying out isn't going to do the job.
In both cases, I use a little
Atheletes foot powder it. don't pour it on heavy. but a very light dusting all over the affected areas.
You might try to blow some vs shake and pour... a powdery mist to coat the affected areas.
That's worked in the past on my seedlings of all types.
It's about as gentile as it can be and if done right will not affect the young seedlings.
As a preventive, air out and lower the humidity in the containers as the plants have germinated and as long as their fine root hairs aren't damaged you'll be fine.
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Topic: Advice on Trichocereus seedling mould welcome! (Read 8251 times)