The white fuzz on the crown is normal for a lot of cacti. It probably helps protect the crown. I don't see mealy bugs in your pictures but they can be hard to see at the distance in your pictures. Escape pods? The 'pillars' stuck to the wood in the third picture above are dead flowers. The fuzz and left over dead flowers aren't a problem.

Thank you for the reply! It makes sense that those are dead flowers - I poked them with a q-tip and knocked them all off this morning.

The reason I was concerned is that these white parts are very powdery, and I can cause them to fall off just by blowing on them. That dusty characteristic, combined with the appearance of white spots forming around some of the areole, are what got me concerned about pests. I just went outside to get some better pictures of the fuzzy parts, and I spied this tiny red looking spider (circled in yellow) crawling around. Maybe I've got red spider mites too?

Back to the white fuzz: I bought several small succulents at a flea market back in May or so. They have all thrived over the past few months, except for this one (not sure of the species). One of the green things died after I transplanted him into that white pot. The other ones grew bigger after that, until they started dying off within the past 2 months.

I brought the cactus to my place and re-potted it around the same time, so I can't help but wonder if I infected the flea market plant. These pics are from today: notice the little white powdery tufts around where each of the green spines comes out of the body.

The white powdery parts on both plants, and now the appearance of the red spider-looking bug: Do either of these resemble symptoms of pests you fine folks have encountered on your cacti and succulents?

Thanks for the closer pic of the first cactus. I see no signs of mealy bugs. When there are a lot of them clustered together and making fuzz their fuzz becomes sticky. The natural fuzz on your cactus probably is water repellent and shouldn't be sticky. The red mite might be a concern. However, if that cactus is often outside then the mite might be a random visitor.

The second kind of cactus looks like an Austrocylindropuntia. The white tufts at the bases of the leaves are normal. The soil mix looks like regular potting soil. This Austrocylindropuntia likes a bit more water than the average desert cactus but don't keep it moist all the time. I didn't see how your other Austro's died but I'd try giving your survivors more sunlight. Your plants look like they are searching for more sunlight. Also, repot them in a soil mix that has more perlite/pumice/grit. A soil mix that drains better might help. Then let them dry out a bit more before watering again.

Polypom

I was thinking that second one is Austrocylindropuntis, but it looks very 'week' to me? Am I wrong? I thought that it should have much firmer stem/trunk - but it could be real lack of light, or perhaps var. I am not familiar with; and most photos I have seen don't have 'leaves' all the way down to the bottom part of trunk.

Rina

I agree they don't look as stout as they should be. However, the spaces between the leaves don't look longer than normal. I might be wrong but I think not all plants grow longer gaps between leaves in low light. In low light my Austro's will grow stems that have the thickness of Jack's plants. When I give my Austro's more light the new growth is fatter and looks better for grafting bigger cacti. My Austro's lose their leaves when they become dormant. Sometimes a branch on mine will be dormant during the growing season while the other branch is green and leafy. The lower leaves on the stems in the pics above look aged. We might be seeing one season's fast growth. Or, maybe these cacti will keep growing non-stop under the right conditions and they haven't rested, yet. Jack's cacti might be a non-spiny clone of A. subulata. Whatever mine are they are spinier.

I have seen photos only of non-spiny A. subulata.

Here is my A. subulata - at least that's the ID I got here - last summer:

Same plant this year - after being outside in lots of sun, it doesn't have as many leaves:

Rina

Interesting. Jack's plants and mine look etiolated compared to your plant. Looks like the branches on your plant grow at the same time. I'll take pictures of mine to share tomorrow.

1. main plant

2. branch cut from bottom of main plant

3. new plant from local store

They are staked because they have a tendency to lean after they are repotted. I changed my mind. Now my plants and Jack's don't look etiolated.

OMG, notice the label highlighted at the top in yellow: Cactus Strawflower. Looks like they forgot to glue the fake flower on this one. I'd take it back. ;-)

Polypomp

I see some difference between your plant and Jacks:

Yours on left, Jack's on right.
I don't know it Jacks is etiolated, or is it different variety?

Rina

I can't be sure. I'd have to compare Jack's plants and mine after growing them in the same conditions. I'm leaning to them being the same species, possibly a different clone, but Jack's are skinnier than they would be in more sunlight. Seems like I've seen pics of Jacks plants before. Seems like there's a website with a list of Austro cacti and pictures I'm missing.

The first picture shows what looks like frostbites. The "pillars" are flowers which failed to pollinate. If they did, they would have a wide base and fall-off only when ripe, giving many tiny black seeds. The offshoot looks healthy, it could have been the cactus was lying somewhere close to the ground and some bugs ate portions of the ribs. Do you see the ribs actually have missing portions, or did the skin just dry-out?

If you're concerned about spider mites, this is how their damage looks like:

http://www.cactusnursery.co.uk/RedSpider.htm

The damaged skin turns into a rusty-color bark. Often cacti recover from that scenario and show a healthy growth tip like the Lopophora pictured in that page.

This is my cactus (Coryphanta?) which suffered from spider mites last year. Plant roots looked sturdy (the plant did not come-off when I nudged it) so I figured it could be an above-ground insect. I watered it overhead (Mites don't like humidity) and in the spring a new growth tip emerged. Now, a whole new section has grown above the old bark.

@Polypom @Rina

Thanks for giving me a hint for the species, as well as sharing the pics of your plants! You're right, mine have no spines nor prickly parts whatsoever, and they aren't near as thick or rigid as yours look. I had never seen this type of plant, and only bought it because I thought it was neat. Maybe I bought the genetically inferior result of some mad botanist's cross-breeding experiments? :-x

As for sunlight and etiolation, I honestly don't think that's it because I've been growing my A. Subulata in the same conditions as my other succulents, same July - October sunlight on my back porch. In fact, they were all sitting in a row on the same porch railing throughout most of this. I typically use the "finger dipstick" test to determine when I should water, but I've kept these plants dry for the most part. Maybe they get watered once every 6 - 10 days at most?

The plants pictured below in the black plastic containers are the ones I bought at the same time from the flea market lady (this was dated 7/18/2015), with the baby A. Subulata in the middle. It's a blurry camera pic, but I'm pretty sure I had 5 - 6 of the plants in that pot when I started.

...and these are those same plants now, with the little black container for reference.

I'm pretty sure I used the same Miracle Gro "Cactus, Palm, & Citrus potting mix", for these, but it's possible I cut it with Fox Farms Ocean Forest potting soil (I probably did for the big cactus just due to the size of the pot). I know that's not ideal for a desert plant, but surely poor drainage / incorrect perlite mixture would have made my babies pictured above look like this sickly baby pictured below!

Maybe A. Subulata is more finicky or sensitive to something in this N.C. weather? I repotted all of those flea market plants the day after I bought them...I didn't know that A. Subulata was many plants, so I was surprised when they all came apart in my hand when I pulled them out. One of the A.Subs died within a couple of weeks of me re-potting, but I chalked that up to my novice plant-handling skills. The others held on, but then started doing the "loch ness monster" dip/grow back up/dip more/grow up/die cycle since maybe late August or so?. That's why I suspected disease or pests, just because it took so long for them to start declining...but maybe they hated that soil, and it's just taken them this long to say "I give up" and die?

@Asclepiad_Fan
I didn't see what my mom did with it on a day-to-day basis when she owned it, but it always stayed in a pot either on the back porch (wooden, 2nd story off of the ground) or inside in a window sill in the winter. Honestly, it's always had some form of scarring and it's only gotten worst as time went on (summer or indoors!). Anyways, here's some pics in bright sunlight (maybe it will show something that my previous rainy-day pics don't?)

This is the front, where there is less scarring visible:

This is the back, which looks worse:

And here is a close-up of the off-shoot: even its base is showing that same scarring!

Not sure if it matters, but this guy has always had more spider webs on it since I assumed ownership and re-potted it. Some mornings, I would see one - two threads on the other succulents, but this guy has always consistently more inside of his pot compared to the other porch-rail succulents. Is it because it's a bigger pot / firm spines make better anchor points and the spiders look for that? Or, maybe I do have some spider-mite like pest? It sure looks like something has been sucking this poor dude dry his whole life...

Did your potting soil have fertilizer premixed with it? That might explain the long growth of your Austro's in one growing season. The dipping and growing back up probably was caused by repotting them. If I repot my Austro's and don't stake them then they do that too until they grow new roots and settle in to their new pot.

Your Austro's don't look sick but they look odd. A. subulata is variable. I thought you might have A. subulata but you might have something different. Someone once pointed me to a webpage about Austrocylindropuntia that had a pic of a plant more like yours. The species name was different but other websites listed the species as a synonym for subulata. Currently, I can't find the website.

Do your plants get direct sunlight during the day or only in the morning/evening? Your four succulents don't look etiolated but they don't have as much color as I expect they'd have if they were getting direct sunlight. If you try giving them more direct sunlight then you should gradually increase the light. Don't sunburn them. I see some red colors in the leaves and stems of your Austro's so they might be getting enough sunlight. However, Rina's plant and mine are getting a lot of light and they have no red.

I'm not sure if that is scarring, corking, or a combination of both, on the large cactus. Any way, it can't be undone and corking will naturally continue as the cactus grows. I don't know the species of that cactus or where it naturally grows but I wouldn't be surprised if they look like that in the wild, too. The parts of the cactus epidermis that are green aren't discolored and look healthy. There is a clear margin between the brown parts of the epidermis and the green parts. That doesn't look like spider mite damage.

Jack

I prefer really gritty mix for all my succulents; most of them (more than 90% of all my plants) don't have any soil in the mix. I have some in mix of perlite and grit; some in perlite & turface; some in grit& turface and many in perlite, grit and turface.

I really can't tell what exactly your plant is; sometimes, the growth is weak because of too much moisture. Your plant looks almost like hardy Sedum rupestre Angelina...either etiolated, or loosing many leaves - I am not saying that it is...

Your plants have grown nicely. If I may suggest, the Haworthia is over-potted.

Rina