Rot on cactus cuttings? Part 2

[treefingers]

I recently posted about rot developing on my cacti here (http://www.cactiguide.com/forum/viewtop ... 24&t=38819). It's been about two weeks since I did the cuttings and I've noticed some discoloration again. I've attached cactus cutting #1 - two views and the second cactus cutting. Does the black coloration mean that the rot is still present and I need to cut again? Is cactus cutting #2 even salvageable? Please help.

[7george]

Yes - cut those again and sharpen that bottom part of the cuttings (ribs cut in an angle). Use clean sterile knife - until cactus tissue looks clean. Sterilize your tool after every cut. You can also apply some fungicide or sulfur powder (or mixed with rooting powder) to the fresh surface. I prefer to cut higher (shorter) because younger stems root easily. Put cuttings in warm and dry place, indoors (not sure about your climate/location), et least for the first weeks.

[treefingers]

Thank you! Going to cut again in hopes the rot does not come back, this will be my third time . I'm located in Toronto so it's finally starting to warm up here but it's not consistent (the weather has been in the 50s-60s these past few days). What's the reasoning behind sharpening the bottom part of the cuttings, out of curiousity? Thanks again!

[hegar]

Combating a rot is not an easy thing. If you do have a large enough plant, it can be done successfully though. It all depends on how far the rot has already spread and if enough of the tissue is removed. On your image 3, there is a dark splotch in the 9 o'clock position. This indicates, that the microorganism causing the rot has advanced to at least that location.
It is of utmost importance, that at least the last cut be made with a steril knife. Once you cut above that point - and there is absolutely no discoloration visible - go ahead and sterilize your knife and cut one more time. With a big plant like yours, you could most likely cut at least one to two inches away from the healthy looking tissue. If the rot organism is still not totally removed, the rot will start again and continue on upward toward the tip of your plant. Fortunately, your Cereus is a fast growing plant and will be tall again within a short time.
Sulfur application will help to slow down a fungal infection. However, If your plant does have a bacterial rot, it will not do much good.

Harald

[treefingers]

Hi Harald,
So I cut well above the areas of rot, with a sharp knife sterilized in 99% isopropyl alcohol (made sure to sterilize each time), sprinkled the tips with sulphur, hoped for the best again...but it's been 3 days since I did the cuts and one of the stems has turned black immediately at the bottom - the problematic one in image 3 (the shortest stem). I'm guessing that one might be a goner but I have cut it again. This has proved to be quite difficult, cutting and waiting and hoping for the best each time. Really hoping the plant can be saved. If it is a bacterial rot is there anything else I can do?
Thank you.

Combating a rot is not an easy thing. If you do have a large enough plant, it can be done successfully though. It all depends on how far the rot has already spread and if enough of the tissue is removed. On your image 3, there is a dark splotch in the 9 o'clock position. This indicates, that the microorganism causing the rot has advanced to at least that location.
It is of utmost importance, that at least the last cut be made with a steril knife. Once you cut above that point - and there is absolutely no discoloration visible - go ahead and sterilize your knife and cut one more time. With a big plant like yours, you could most likely cut at least one to two inches away from the healthy looking tissue. If the rot organism is still not totally removed, the rot will start again and continue on upward toward the tip of your plant. Fortunately, your Cereus is a fast growing plant and will be tall again within a short time.
Sulfur application will help to slow down a fungal infection. However, If your plant does have a bacterial rot, it will not do much good.

Harald

[hegar]

Although there are several bactericides, which the home gardener could use, I do not know how effective they are. Also, I noticed, that the price for them is quite steep. That may explain, why they are not used much.
You are just trying to have a cut heal, without allowing microorganisms to re-infect your plant. For that purpose a sterile cutting tool should suffice.
If bacteria or fungi have already progressed into the tip of the stem, then neither a bactericide or a fungicide application at the cut end will be doing any good. All you are trying to do is to sterilize the cut surface until the wound has healed and a protective skin been produced by the cactus.
While a systemic fungicide or insecticide can be taken up by the plant's roots and leaves, I do not know, how well it would be translocated to the cells of the entire plant by surface application to the cut end.

Harald

[treefingers]

Thank you, Harald. Woke up this morning to discovery that one of the stems has developed some black at the tip, will cut it off but I'm guessing that is not a good sign.