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Removing Rot from Cacti and Succulents
Cacti and succulents are prone to a fungal condition commonly called black rot, as well as mildew and other fungal diseases. It may start as a little spot, or perhaps you will notice the base has darkened. No matter how it first shows up, cutting it out of the plant is sometimes essential to saving it. Below is first, an example of cutting the black rot spot out of a pad from my favorite opuntia, Opuntia macrocentra (violacea), otherwise called a Purple Prickly Pear. The second demonstration is for Sanseverias, presented by Jeanette Haygood.
In this Opuntia example, the rot started as a spot, very defined. This is sometimes called "shot-hole" rot as it resembles shooting a hole through the cactus when it has rotted through.
I have also had black rot start on my Epiphyllum oxypetalum, the Night Blooming cereus. In that case, it was very small spots here and there on the leaves. I at first treated that with a fungicide, but in areas where it spread, removed the leaf portion or entire leaf.
When choosing a fungicide, a standard garden fungicide will do, usually they are sulfur based. Follow the label directions as to what plants the fungicide is safe for, application methods, and toxicity recommendations.
In addition, a home remedy that has natural anti-fungal capabilities is cinnamon! See the lower half of the page for examples of mildew and black rot damage on Sanseverias, and how to trim these beautiful plants.
Treatment for fungal diseases:
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1. Treat the plant with a fungicide ( a commercial product or cinnamon). |
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2. Improve air flow around the plant and make sure it is not remaining damp for too long after watering. |
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3. If necessary, improve drainage of the soil by amending it with construction (coarse grain) sand. (see the culture page on soil ingredients) |
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4. If the rot is continuing to develop or threatens the life of the plant, it's time for "plant surgery". |
Demonstration 1 - Opuntia
Opuntia macrocentra - the section cut from it has the obvious black rot. A small section shown here in the center of the scan was also cut out as there was traces of rot in the inner pad area. To make a cut like this, use a sharp, sterile (clean with rubbing alcohol) knife to make a clean cut. Try to angle the resulting wound so that rain and /or watering will drain off naturally. I could have cut the bottom right portion completely off to improve the rain drainage.
This is the piece that is cut off initially. It would appear that I have removed all the rot, but....
checking the inner fleshy part of the plant shows how it has permeated from the first piece cut off (on the right) to the second portion removed (on the left)
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This is the second portion. I could have tried to scoop out the rot, but I prefer to completely remove all signs of rot. This gives the plant the best chance of recovery.
This is a close up of the round initial "rot spot". Charming, isn't it?
Finishing the Operation
Some people dust the wound of the plant with a sulfur dust. A local nursery should stock this. I don't do this myself, but it doesn't hurt. What I do is to let the plant dry out for a few days or a week. I can do this with a pad section of an opuntia. If you are working on a potted plant, do not water for approximately two weeks, depending on the variety.
With my opuntia pad, after drying, I pot it up in my basic cactus soil mix. I had not removed that little bottom section, so I am careful that it is above the soil level, in order for me to make sure it does not hold water and, well, you know, rot.
My funny looking potted pad then is placed in a brightly lit (but not hot) area and let to sit and rest for awhile. In approximately two weeks, I will water it just a bit, and I will use very careful watering until I am sure it has re-rooted. As always, follow the culture needs of the variety you are working with as far as watering, but a general rule is that with cacti, if in doubt, don't water. After all, these plants are famous for their ability to survive and thrive in less than ideal conditions, and until roots have formed or a scar has formed over the cut, it is better not to water heavily.
Demonstration 2 - Sanseveria
all below photos copyright 2001 Jeanette Haygood
Leaf spot damage on Sanseveria - dust small areas like this with a fungicide.
Mildew on the leaves of Sanseveria
The plant with mildew affecting its leaves
Use sharp clean scissors to cut the damaged leaf area away
Close up of trimming the leaf
The trimmed plant. The cut edges can be dusted with a commercial fungicide or cinnamon to prevent re-infection.
The leaves will not grow from the cut area, but will continue to grow from the base, eventually growing to their previous height, healthy and happy. :)