Please help me save my Cacti!

[Storm]

Hello everyone.

I'm pretty new to keeping cacti... I was bought a pot with 3 species in it as a gift by a family member a couple of weeks ago (they bought them at a local garden centre) to keep in my studio, and they do not seem to be at all well... I was planning on re-potting them as the stones have all been glued down into the pot (for presentation rather than practicality I guess) so I can't check the soil quality, etc; but didn't want to move them until I know what is wrong with them. As far as watering goes, I've only watered them once so far since I received them. (and was going to do so again today but avoided it as I don't know what is wrong with them yet).

The first problem I noticed was with the dark green one with the red spines (not sure if this is actually a cactus or Euphorbia enopla) - It had small white indents on it when I was given it, then it's spikes started falling off and has very quickly started to dry up, shrivel and turn brown!

There is some almost web-like substance on the side of the fluffy cacti (I'm not sure what species he is)... could this be evidence of a pest like spider mites? I have inspected them thoroughly and can't see any bugs on them, but I'm going to buy some insecticide to treat them with anyway just to be safe... is there a specific recommended type I should look out for or will any type do? I don't want to accidentally poison them with the wrong stuff!

The final problem I have noticed is on the lighter green cacti with orange/brown spines (I'm not sure what he is either... I need to spend some time browsing through the database here to ID them ^^)... there is black around the base of one of them. I'm really hoping this isn't rot!






I've also got a succulent plant that seems to be having problems... I've had this plant a little longer (just over a month now), and it was OK until about 2 weeks ago, when the tips of the leaves started browning. I'm not sure if this is corking caused by it not getting enough water (I was giving it one main watering a week plus spraying a mist of water onto it every few days)... I'm planning on upping the water I give it to see if it helps - does that seem like a good idea? I don't know if it requires more water as it is trying to flower... the new growth seems fine; but the old leaves have all browned at the tips.





These are all indoor plants... I just took the pictures outside so they were clearer.

Thank you so much for your time and help - I really appreciate it; and hopefully I will be able to get these plants back to full health soon!

[hegar]

The Euphorbia does have a rot. You may have to either remove that stem completely or at least cut away the discolored part, including about one half inch of the healthy looking tissue. It looks though, like the best treatment would be to take that stem off, because the rot has spread too far already. The blue-green cactus with the red circle also may have a rot. Try to feel, if the affected area is soft. Usually, the rot is most noticeable at the bottom and moves upward.
I would remove all the plants and take a look at the root system and examine each stem for the presence of rot. If there is a rot, you may still be able to save the plant, by discarding the lower, rotting part and keeping the upper, healthy part to get rooted again. It should take a week or two for the cut part to heal and form a callus. Then you can go ahead and plant the stems into a good cactus medium, i.e. very little organic matter and coarse, well draining material as described when clicking on the tab "Growing Cacti" on top of this page.
It seems, like you did water your plants a little too much. The succulent pictured last also may just show some water damage on its leaves.
Whatever you decide to do, if this is a rot, you have to act quickly, because the organism does spread pretty rapidly and when it reaches the top of the plant, it is too late. So, give your plants a good examination and then take corrective action.

Harald

[Storm]

Thank you so much fr the help and advice Harald! You're a star!

Luckily the stem with rot turned out to be growing separate to most of the other parts of the Euphorbia so I could just remove the affected one from the pot... I cut off the healthy parts and will attempt to re-plant them when they are ready.
I did notice, however, that two of the other stems had brown discoloration:



Is this also the start of rot, or something else? If it's rot I'll cut the tops off of these ones too, I just didn't want to mess with them if they were OK.
Also, there is this weird damage on the side it has had since I got it that is covered in dried sap:



Is this anything to worry about, or is it just cosmetic?

The black portion of the blue-green cactus does not appear to be soft and has not really spread so I'm not sure if it's a rot...



...When I was re-potting it a bit flaked off and it was almost scab-like. If it gets any bigger at all I'll immediately cut off the top of the cactus to save it... but is there anything else this could be? Or is it just a slower-growing rot that I should remove ASAP?

Thank you again for all the help and advice you have given me so far - I really appreciate it!

[hegar]

Hello Storm,
I have found Euphorbias to be a little more difficult to grow than cacti and do not have any in my succulent collection. So I am going with what I would do with a cactus and apply that to the Euphorbia. I hope, that it will work for those plants too.
The darkened areas near the soil surface may not be something to worry about, as long as they do not grow or turn soft. Sometimes they are just a scab. The same can be true for the cactus with the scab near the base of the plant. I would keep an eye on those lesions though.
Whenever you do cut away a diseased part of a cactus or Euphorbia, make sure, that you remove anything that is discolored, then dip your knife into some diluted bleach solution (1 part clorox bleach and 3 parts water) or wipe it with rubbing alcohol, before making yet another cut into the healthy tissue. That way you do not leave any bacteria or fungi on the cut surface, which would be able to continue the infection. Then let the cut plant surface heal, until I nice parchment like skin has formed (callous) before planting the healthy stem in fresh growing medium. You can also apply some rooting hormone to help the plant form roots, right after you made the final cut. These chemicals sometimes do contain a fungicide, which will give additional protection for the cut surface.

Harald

[tomo]

I'm curious, are Euphorbias the ones that have the dangerous sap that we need to be careful re: not touching our skin/eyes? I'm still a newbie so I'm curious about that sort of thing, how to cut/save a cacti without touching the sap, etc.

[teo]

The white latex sap from Euphorbias should be avoided but it's not dangerous if you just get a drop on the skin. It can be (moderately) poisonous if you swallow it but mostly it is an irritant and can cause some pain if you rub it your eyes.