PLEASE, PLEASE, PLEASE ... Not SURE if it is sick or not, but JIC ...

[WayneByerly]

i've NO idea ... i'm just stumped ... like everyone else ...

[Wise guy]

Wayne, I don't have any personal experience of this problem, but have a look at a physiological problem known as oedema or edema.
It has to do with a water inbalance in the plant, and is more prevalent in humid conditions. Hope this may help with getting you closer to a diagnosis.
All the best, Mike

[stefan m.]

Doesnt look like it. Wise guy this is definitely some kind of plant surface pest.

[WayneByerly]

... have a look at a physiological problem known as oedema or edema.
It

Mike: I looked at 6 webpages, and of all the possibilities that have been suggested, I think this one comes in last place as far as likelihood goes. I very much appreciate your providing me with a link to a possibility, but I just don't think this is it. What few pictures there were showed something that looks completely different than the pictures I've posted. Thanks for taking time out of your day in an attempt to help me out with my problem. I really do appreciate you and your willingness to try and help out.

[Wise guy]

My pleasure Wayne, I hope you find a solution soon. Mike.

[WayneByerly]

... definitely some kind of plant surface pest.

Stephan: and as many pictures as I have seen of the damage done by RSM--and there are many, many more of those--neither do they look like the damage shown in the pictures that I have posted. I have always found you to be a reasonably knowledgeable person regarding cacti. Any other ideas?

[7george]

It looks like some kind of fungus to me...

[brixtertabun]

Deleted

[WayneByerly]

My cactus also had this ... . I didn't see any crawling insects with my naked eye.... .

You're the first person to tell me anything that sounded reasonable. What I have is quite definitely not red spider mites. Is there anything else that you can tell me about what was wrong with your Cactus? You have any pictures of it?

What's the difference between red spider mites and fungi?

Red Spider Mites is a bug and fungi is a well... fungal growth.

[brixtertabun]

Deleted

[stefan m.]

People keep saying red spider mite means spiders walking around, but i doubt it. I dont think youll see mites themselves but the damage they leave. Also, webbing appears on leafy plants.

[WayneByerly]

Let me rephrase my question. How can I tell if the pest on my cactus is red spider mites or fungus?

1) Go to http://www.google.com
2) execute a search for "red spider mites on cacti"
3) click on "images" somewhere in the upper left hand quadrant of the screen

You'll be shown lots of pictures that you can use to determine whether or not you have RSM on your cacti. Click on "All" in upper left hand quadrant of the screen. Browse thru/read articles concerning RSM.

[WayneByerly]

... I dont think youll see mites themselves but the damage they leave.

That's a good picture of the damage that spider mites leave. They eat the upper cells off of the skin of the cactus leaving little dry tan places etched into the surface of the cactus. Look close at the pictures I posted and you'll see that the stuff I'm talking about looks like it's been applied-to-the-surface/painted-on-the-surface and not etched into it.

[jfabiao]

710461612-RSM.jpg (149.87 KiB) Viewed 1413 times

You'll see the mites if you pick them at the height of the attack. What often happens is that people only notice them after the damage is done, and then there's no point searching in the damaged area because the mites have moved elsewhere. If you have just a few plants, you'll also learn the signs of the first attack - a sort of paleness to the plant around the crown. A magnifying glass will reveal the mites and you'll be in time to catch them before they cause much damage.
WB, your plant seems to suffer from some kind of fungal disease, usually referred to as "rust". If that's what it is, it's down to growing conditions and it will fix itself (i.e. will stop spreading and leave you with a scarred but healthy plant) if you change them. Try and reduce atmospheric humidity (perhaps increased ventilation?).
One final word for treating the plants for conditions they don't suffer from: it's a very good way of making sure you WILL have that same problem somewhere in the future. Pest resistance is a reality you don't want to have to deal with.
(the plant on the photo has since recovered, albeit badly scarred. As it happens, Lophophora grow in such a way that this kind of damage eventually dissappears below ground)

[stefan m.]

Just in case, use insecticide, and try to scrape of as much debris as you can without damaging the plant.