Dark Lumps in Cactus

[Briscactus]

I noticed some dark lumps on the side of one of my plants. They seem to be embedded in the plant and possibly growing out of it. I removed a couple and there doesn't seem to be damage underneath. Any ideas?

[hegar]

It is about impossible, to tell for sure, what kind of problem spots your cactus did develop. However, if it is a disease, it should result in either more spots to appear and/or those that are present to increase in size.
There is a section about Cactus Pests at the home page of CactiGuide, which does show a few things (signs, symptoms, etc.) of cacti in trouble.
One is a photo that I placed there, which does show an ascomycete fungus. I have seen that fungus thus far only on Echinocereus spp.. There is yet another fungus, which seems to be rather virulent, and also attacks cacti. I did spot that one on a Ferocactus wislizenii. That fungus was identified as Fusarium sp. a hyphomycete fungus or imperfect ascomycete.
I am attaching a photo of the one pathogen found on Echinocereus.

Harald

http://www.cactiguide.com/graphics/pest ... _a_200.jpg

[Orion Drakkar]

They look like dried flowers

[Briscactus]

They are pretty close to flowers in terms of position and look. My only hesitance to think they are is that the plant hasn't flowered (usually it does later in the year).

[esp_imaging]

They look like dried up buds that never developed fully. It's quite normal with Mammillarias and similar species that not all of the buds develop fully into flowers. They can persist for a long time, they may not be recent.

[hegar]

I do not have many Mammillaria spp. and I have not had aborted flowers show up on my M. grahamii. However, Orion Drakkar, Bricactus, and esp_imaging may be correct with their assessments. Because Mammillaria cacti do produce "rings of flowers", the dark lesions should the be arranged accordingly.
I have to admit, that the tissue around these spots does not show any discoloration, which would usually be present, if a pathogen is causing the lesions. As long as the spots do not increase in size or multiply, there should not be anything to worry about.

Harald