Hallo, everybody,
I have a Gymnocalycium horstii that started with (for me) strange patterns. It looks a bit like cork:
Additionally he has some pale areas. As if the strong summer last year was too strong for him.
Is this normal? Or is it possibly a fungus? Any idea?
Thank you for your help
Ruth
Hello Ruth,
your cactus might indeed have been exposed to just some environmental factors (i.e. weather) that it was not used to. Corky lesions can occur as a result of many different things from mechanical injury to burning of the plant's epidermis by sun rays or chemical sprays. The major spots are between the ribs which is where the plant will be more shaded and water could remain longer before evaporating. A fungus will develop where it finds the most beneficial conditions, a lot of times where the host plant has already been weakened. If your lesions do not spread or enlarge and there is no softening, indiating a rot, you only have a cosmetic problem with your Gymnocalycium. I do have some native cacti in the ground that look a lot worse and seem to have a problem adjusting to their environment. Fortunately, plants in general and cacti in particular, are conditioned to survive even adverse conditions.
I'm going with spider mite on this one. That's just the sort of place they like to hide and not be noticed, probably last winter or even earlier, then the plant grows and the scarred area becomes visible.
Hello Ruth,
what Ian implied can of course also be correct. Sometimes it takes quite a while for damage to show up on a plant. It could be that spider mites were at one time present on your plants and feeding in the recessed areas. If they are still present you will most likely see additional damage in the future. The first thing should be to always take a very close look at the abnormal looking area. Spider mites are rather small, but you should be able to see them with a magnifying glass. You could go ahead and use a brush on the affected areas, brush everything on a white piece of paper, and examine anything that collects on it. The mites do move around but very slowly. On the other hand, there may not be anything present at all. Observation of any change of the plant's appearance would be grounds to worry though and require immediate action on your part. Just judging from my years of experience, corky spots are usually only the plant's reaction to some injurious agent like a scab on a wound of a human being and present on practically all wild collected cacti that come into my office.
Thanks, Hegar and Iann,
fortunately it does not look like an invasion of spider mites (I am just fighting off mealy bugs of some Orbeas etc. and I really am fed up!).
The corked areas do not enlarge or spread, and ther are no soft spots. So I hope the plant has no fungus.
Last summer was pretty hard in the beginning: a Lophophores nearly got cooked within very short time. As the plant has lighter areas plus these corked ones, I now guess it really was that short period at the beginning of last summer before I installed a sunshade that caused the change.
Ruth
