Saturday, January 31, 2009

Question for the Hive Mind: Cereus peruvianus blotches

Bad news would be good news on this one. I've had two large Cereus peruvianus since 2004, and they did really well for me for quite a long time, tripling in height the first year and then growing more slowly thereafter. Never any problems, until they got mealybugs a couple years ago. I fought and cursed and agonized over the mealybugs for a good solid year and a half, at least, before finally managing to get rid of them with a systemic insecticide (imidacloprid) and neem oil and regular rubbing alcohol sprays and leaving them outside for the summer (they grew a foot in those few months).

Another such victory over the mealybugs and we are undone. But I digress.

So the situation now is that, one, the plant is sticky. Not sticky in the covered-by-honeydew sort of way. It's more tacky, like paint that's not completely dry. This has been the case since the plants came inside last October or November, and is apparently not going away. I've been assuming that it was probably related to the rubbing alcohol treatments in some fashion or another. The other weird thing that's going on is that I'm seeing odd tan-to-gray patches appearing on the stem. The worst of it is concentrated on one particular side of one particular rib of one particular plant, but these patches are all over. I don't know what this means. Picture of one of the biggest spots:

I think what I'm wanting to hear is that this is something terrible and irreversible but basically superficial, and that I should re-start the plant from cuttings of the stuff that grew last summer. But I'd also like to know, for future reference, what these patches actually are, how they got there, and how to prevent them in the future. Anybody have any ideas?


jodi said...

I seem to think this is merely a physiological thing, but I'm not completely sure. Maybe Carol at May Dreams Garden would know; she has a night-blooming cereus.

Fr3d said...

The book I have states that brown, corky areas at the base of a large, columnar cactus are simply signs of aging.
Also, the same thing on other types of cactus could mean any of the following: damage from handling, poor ventilation, sun scorch or sudden changes in temperature.
The book goes on to state that nothing can be done about such damage, but it will not spread.

mr_subjunctive said...

I'm not positive that it hasn't been spreading; it seems like there's more of it now than there was, but I haven't been watching very closely. At least now it's been photographically documented, so I'll have something to compare to later.

It's also not just at the base of the plant (or even mostly at the base of the plant), so the temperature theory is looking pretty good to me right now.

Anonymous said...

That doesn't look like typical columnar cactus aging. It wouldn't have come on so quickly anyhow...that stuff takes a long time and it's not usually on ribs like that.

from the picture it kinda looks like sunburn, but sticky doesn't really seem to fit with that. good luck...