Quickly-Spreading Ariole Spots

[Aichybatoal]

I already posted about this just a few days ago, but the problem has grown exponentially in just one day. On many of the arioles of my Echinocactus Grusonii are brown, sunken splotches. I at first suspected sun damage, but I now think that's impossible, because these ONLY occur on/around the arioles, and they are not on one side of the cactus - they are evenly and randomly distributed. Yesterday, there was only one. Today, there are about eight. I also can likely remove pestillence as the cause, because I can see no insects, parasites, or particles of any kind near the areas of affliction. I realize that there are insects that reside in the plant's roots and cause damage that way, but if this were the case, I don't think that the damage would be seen on the arioles. Anyway, PLEASE try to give advice, experience, and assistance to me and my Golden Barrel. We'd both love to rid ourselves of this blight.

[oldcat61]

I'd go ahead & spray with a contact killer - could be spider mites or something else you can't see. That's where they start. Then I'd use a systemic like Bayer. Sue

[Aichybatoal]

I don't have either of those! Should I really buy two pesticides, or can't I do something else?

[Pilif]

To me it looks and sounds ("appearing suddenly") like stress 'damage' (sun, temperature, ...).

If you want you can try and look for insects with a magnifying glass.

[hegar]

It could be sun damage. After all the areoles are located on the ribs, which tend to receive the most sun burn. Also, are these beginning spots exclusively near the top of the plant? The plant's epidermis is more sensitive there and will burn more easily.
Was the cactus purchased recently and then placed into full sun or was it in a protected area and then moved to one with more sunlight?

Harald

[Aichybatoal]

Yes, it could be sun damage. I've never stored my cacti outside until this year, and I know I should have introduced them slowly, but I didn't feel like putting canvas over my greenhouse, and since I put them out this spring, I figured the sun was weak enough to be an adequate introduction. I REALLY hope tins just sun, because I don't want to have to deal with red spider mites, and sun damage does seem pretty likely. I will keep you updated and posted on all developments. Thank you very much for your thoughts.

[Aichybatoal]

It could be sun damage. After all the areoles are located on the ribs, which tend to receive the most sun burn. Also, are these beginning spots exclusively near the top of the plant? The plant's epidermis is more sensitive there and will burn more easily.
Was the cactus purchased recently and then placed into full sun or was it in a protected area and then moved to one with more sunlight?

Harald

I suppose you could say they're beginning on top. It would be more accurate to say that they are heavily concentrated on the top half of the plant. Also, it was not purchased recently, but I did fail to give it an very good introduction to sunlight. Again, I very much hope that it is sun damage, and not red spider mites. Thank you very much!

[Aichybatoal]

The latest news: I kept my cactus indoors yesterday and today as a test to see if it really was sun damage. If it were sun damage, then it would not have spread. If it were a pest, then it still would've spread indoors. Luckily, there are no more spots today than there were yesterday, so I can safely assume that it is, in fact, just some sunburn. Now, I know that sun damage does not really heal, correct? I mean, these little spots will be visible on the plant for the rest of its life, right? That's alright with me, because they're small and on top of the arioles, so they're not very visible, and no cactus is perfect, ya know?