Hi there 808, I would say it is either the eggs of some sort of pest, or you have a terrible fungal infection going on. Either way I would get the plants out of the media as soon as you can. Have you examined the leaves or roots of the plant yet?

Tracy

Hi Tracy,

I took the plants out of the soil and washed the roots. They were also suffering from a mealybug infestation, so there was damage to the leaves -- some were yellowing and dying -- but I'm not sure if that was caused by the mealybugs or the yellow fungus stuff. I've found similar yellow stuff in a couple other pots. This pot had the most extensive infestation. The soil was moist, but not soaking wet. I removed the mealybugs, removed damaged leaves and stems and washed the roots of the plant. The root system didn't appear out of the ordinary. The yellow fungus is not visible until I dig up the plants because it's underground around the roots. Some of the stems on the plant (Portulaca Molokiniesis) were shriveling, but, again, I don't know if that was because of the mealybugs.

808
What are the soil ingredients?
It looks like there is lots of organic matter, large pieces of mulch? I can't tell from the photo.
I have used mulch in the pots (mixed with peat etc.) few years ago - before I got to GardenWeb -, and found it getting moldy most often.

Tracy - Thanks for the additional information and the reference.

Rina - I used a mix of Miracle Grow Cactus/Succulent and pumice. I've since revised my mix and put in MG, Turface, Perlite and some pumice. I found a similar problem listed in a marijuana-growers forum and the guy there was also using MG.

Rhizo - Thanks for the detailed information. I'm going to re-pot the affected plants. They weren't doing well anyway, maybe because of the texture change you mentioned or possibly just because of the mealybugs.

Don't believe them to be mealybugs at all.