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I have a M. melanocentra (for id info, see thread viewtopic.php?t=19283" onclick="window.open(this.href);return false;). There is extensive browning around the base. It seems too extensive to be corking and too well patterned to be phototoxicity as shown on http://www.cactiguide.com/cactipests/#corking" onclick="window.open(this.href);return false; . Can my cactus be helped? (Sorry about the photo's rotation.)

homerjay4 wrote:I have a M. melanocentra (for id info, see thread viewtopic.php?t=19283" onclick="window.open(this.href);return false;). There is extensive browning around the base. It seems too extensive to be corking and too well patterned to be phototoxicity as shown on http://www.cactiguide.com/cactipests/#corking" onclick="window.open(this.href);return false; . Can my cactus be helped? (Sorry about the photo's rotation.)

20140608_100542[1].jpg

Could be flat mites. Also called false spider mites because they don't spin webs -- impossible to detect with the unaided eye. I've had run-ins with flat mites before, although if you live in a dry climate, we can take that possibility off the table. If you're living in a high-humidity area, I would definitely suspect that you've been dealing with flat mite infestations for some time and you didn't even know it. In which case, Bayer Advanced 3-in-1 spray or TetraSan.

This problem started quite some time ago (at least a year) when I lived in NW Florida, certainly a wet climate. Since January I've lived in Albuquerque, NM though, and it's been quite dry with maybe 3 small to medium rainstorms total. The wet season is coming up though, I'm told, whatever that means in the desert.

homerjay4 wrote:This problem started quite some time ago (at least a year) when I lived in NW Florida, certainly a wet climate. Since January I've lived in Albuquerque, NM though, and it's been quite dry with maybe 3 small to medium rainstorms total. The wet season is coming up though, I'm told, whatever that means in the desert.

NM has the wrong climate for flat mites, so you're lucky there. Such being the case, I have no ideas about what could cause the extensive browning.

Has its rotation relative to the sun been changed? That may have caused sun burn/stress and the started corking.

Would it be useful to replant the cactus with the browned part below the dirt?

No I wouldn't do that it could just make things worse if it was say down to a fungus or baterial infection. I would have a look at the roots though, get it out of the pot check for mealies and soil quality. Treat anything and maybe new soil if full of salts if you have used hard water at any point or could be exhausted of nutrients and want a bit of new humus. Basically give it a full service.