Something affecting new growth of these Mammillarias

[rodsmith]

Have you de-potted them? I have found that problems in growth (lack of it) or unusual growth patterns are often due to root damage or even root loss or pests. It might be worth a look.

[gerald]

There is new growth so cells are replicating. What's not happening is the cells are not producing proper spination. My guess is that this is caused by a poison that inhibits the formation of spines, maybe from a virus, red spider, or a virus transmitted by red spider.

I had the same problem last year, I'll send some pics later.

This phenomenon may be of use in agriculture. If the cause is located, and used to grow fast growing cacti without spines, they could be used for animal fodder.

[Peter]

I reckon that Diane's right - looks like overfeeding to me. Too many Big Macs makes folk grow abnormally!

[Keith H]

I reckon that Diane's right - looks like overfeeding to me. Too many Big Macs makes folk grow abnormally!

My two penny worth, I am with Peter and Diane on the over feeding theory.

[David48]

Thank you for your suggestion. Five Mamms now have been affected out of about 80 Mammillarias in my collection. The other 75 are fine, as are the other genera, no sign of etiolation, or forced growing. Two of the Mamms have shown signs of some grow back of spines, although I think a disfiguring band is likely to mark the plant. I don't think too much nutrient is a prime suspect. One common factor was their prolific flowering, 4-8 weeks continuously. I am wondering if it was red spider, transported by bees, or a garden plant virus which hits fresh growth, transported by some kind of insect..

[gerald]

I reckon that Diane's right - looks like overfeeding to me. Too many Big Macs makes folk grow abnormally!

My two penny worth, I am with Peter and Diane on the over feeding theory.

Unlikely.

Last year when I had this problem I fed every other week with half strength feed.

This year I feed every week with half strength feed. The plants are actually better for it, and there is no sign of this condition.

I'm convinced that the problem is connected with RSM.

[Keith H]

There is new growth so cells are replicating. What's not happening is the cells are not producing proper spination. My guess is that this is caused by a poison that inhibits the formation of spines, maybe from a virus, red spider, or a virus transmitted by red spider.

Thinking about it, could be secondary damage from the pesticide, rather than primary damage from the pest, be it RSM or other?

[David48]

Thank you for all these thoughts. I am doubtful about the over feeding theory because I followed the instructions carefully, I used cactus fertilisers, first "focus", then changed to Chempak cactus fertiliser, fertiliser only on alternate waterings. If there was something wrong in this regime, I would expect changes to occur in many plants, not just a minority, about 5%. Two of the plants have since resumed spine growth, yet I have not ceased to use the fertiliser.
One of the affected plants was newly potted this summer. The others newly acquired and potted last summer, I had intended to skip this year for them, although M glassii has grown tight to the pot. Thus I am not sure that potting was the problem.
The plants affected had a lot of flowers, over an extended time. It could be that visiting insects carried RSM or a virus and transferred it to and between them. There are garden plants in the locality which have been affected by a virus.
On Mammillaria Forum I see a few years ago there was the same problem reported by a Mammillaria Forum member from Glasgow, only I see on his pictures what looks like RSM discolouration on the plants as well as spine absence. I am thinking if it was RSM, I probably caught it before it discoloured the plant-three other cacti, non Mamms got RSM, and I sprayed the collection with Bug Clear Ultra straight away upon diagnosis after that. Maybe I caught it early on the Mamms.
But I am curious that to my knowledge, only one other grower has directly experienced the same problem, whatever caused it, I would have thought there might be more.
Thank you again for your comments,

[Terry S.]

Hi David48, I have occasionally seen the problem so it may not be so rare as you fear. The cactus that has done it this year is a grafted Echinomastus acunensis after growing happily for several years and developing nice adult spination. I have no idea what the cause is and do not suspect overfeeding or red spider mite. Perhaps it is at the genetic level with some gene getting switched off or on for some reason?

[rodsmith]

I've had a similar thing happen to my young Mammillaria dioica, see photos. Earlier in the growing season about 7 or 8 new tubercles appeared either spineless or semi-spineless. Subsequent growth has been normal. My cultivation regime this year has been no different from normal and none of my other plants has suffered in this way. However, this was one of my plants that was subjected to 13 months enforced storage in darkness between November 2015 and December 2016, which could have had an adverse effect on subsequent growth; although none of my other stored plants has been affected in this way.