Succulent Care Guide: Understanding Viruses, Bacteria, and Fungi in One Article

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The article begins:

Fellow plant lovers, especially the ladies among you, fear nothing more than diseases striking your succulents. No wonder, after all, keeping succulents at home is meant to let these chubby little things look cute and adorable, not to invite some terrifying thing in.

But there's no way around it. Once you fall into the succulent rabbit hole, you must learn to face all kinds of diseases. Not only must you dare to face them, you also have to grit your teeth and treat them. Along the way, you'll also turn yourself from a delicate lady into a tough woman. After all, to face diseases calmly, you must first figure out what caused them.

Let's start with viruses. I think when we grow succulents, we often hang the word "disinfection" at the very edge, but actually that's a bit unfair to viruses. Because the vast majority of succulent diseases have nothing to do with viruses. The disinfection methods we normally use can indeed kill viruses, but our real purpose is usually just to kill fungi.

To put it plainly, a virus is essentially a protein carrying a small segment of genetic material. There are simply too many ways to kill viruses. Most viruses lose their activity at temperatures above 40°C due to protein denaturation. UV lamps, alcohol wipes, potassium permanganate solution, and other methods that can destroy proteins can all easily kill viruses.

It's not entirely accurate to say most diseases have nothing to do with viruses, but most viral infections are not fatal to succulents, because viruses actually live as parasites inside the succulent's body, and of course they don't want their host to die.

A virus is truly a very tiny thing, so small it almost doesn't count as life. The only thing connecting it to life is a small segment of genes inside the virus. Viruses exist solely to replicate this small segment of genes. So when a virus invades a cell, it disguises itself as a segment of the succulent's own genes and hides. When the cell divides, it incidentally replicates the virus's small gene segment along with it. As a result, from our perspective, the succulent isn't sick but has undergone a strange mutation.

The variegation of succulents that we often talk about is partly caused by viral invasion. Some variegated succulent varieties cannot be propagated through leaf cuttings or sowing, also because there are no viruses in the tender cells at the stem tip or leaf meristem (those of us who grow succulents habitually call the meristem the growth point), so the offspring naturally lose the variegation.

Some viruses cause changes in leaf appearance, such as bumps on leaves or changes in leaf shape, and so on.

Sometimes, a firm symbiotic relationship forms between the virus and the succulent, such that the viral genes exist throughout the succulent's cellular genome, together creating a new variety.

Diseases caused by viruses are basically genetic diseases, very stubborn, and even disinfection cannot affect the inside of the succulent. For example, there is a virus that causes the leaves of succulents like Sedum rubrotinctum and Sedum pachyphyllum to mutate, becoming very ugly with many pits and bumps.

Facing such diseases, there really isn't a good treatment. Viruses generally spread through the succulent's sap. If your hands or tools that touch the succulent's wounds during beheading or cuttings come into contact with other succulents, the virus may spread.

Most viral diseases were not contracted on your windowsill. They mostly already carried the virus when they were beheaded from diseased plants. So you can simply treat them as a variety you don't like. The way to deal with them is generally to ignore them and not propagate them in any way. Just let them live or die on their own.

Now let's talk about bacteria and fungi. Fungi are mentioned here rather than bacteria because bacteria and fungi are not the same type of organism. Without giving a very scientific explanation, you can simply think of bacteria as a microorganism closer to animals, while fungi are closer to plants.

Among succulent diseases, those caused by bacteria are few. The most common one I've seen is a bacterium that causes root nodules to grow on the succulent's root system. After root nodules form, they affect the root system's ability to sprout new roots, leading to the inability to absorb water and causing desiccation. The treatment is to trim away the root nodules from the root system, then let it re-root.

Most succulent diseases are caused by fungi. Fungi like to grow in moist and warm environments and reproduce through spores. Killing fungi is easy. UV exposure (that is, sunlight) can effectively kill fungi, and disrupting the fungal reproductive environment can also control fungi, such as keeping things dry.

But the spores produced by fungi are difficult to eliminate. Every spring, in the warm and humid air south of the Yangtze River, countless mold spores drift about. Mold is a type of fungus. As soon as it lands in a moist environment, it immediately begins to reproduce rapidly, forming large patches of mold.

Mold doesn't care what is a succulent and what is a wall. As long as it's a nutrient-rich, warm and humid environment, it's an ideal breeding ground for mold.

For mold, succulent leaves are nutrient-rich and full of water, making them an ideal breeding ground. But in most cases, the succulent's cell walls are enough to block mold invasion. Even if mold invasion succeeds, the succulent can still prevent further mold invasion by blocking the vascular bundles.

Some plant lovers like to keep carbendazim and potassium permanganate always at hand, always trying to kill all fungi, which is impossible. Because mold spores are everywhere in the air. It's not that mold doesn't attack succulents, but that healthy succulents leave no flaws for them to exploit.

When black rot occurs, it's often because there's a wound on the succulent's roots, stem, or some other part that hasn't healed yet, allowing mold to take advantage. In this case, the number of mold in the soil doesn't need to be very high. When they discover the succulent's flaw, just one hypha infecting the succulent will rapidly reproduce until the succulent develops black rot.

Other diseases such as black mold disease, sooty mold, and so on are also caused by mold. Fungicides and sterilization can have some effect, but the fundamental problem lies in the succulent's wounds and its self-repair ability.

Wounds make the succulent itself a prime environment for mold parasitism. But wounds alone don't necessarily lead to disease, because the succulent's body also has an immune system similar to that of animals. The immune system will control mold reproduction and isolate already-infected tissue from healthy tissue. Then even if the wound is indeed infected, it can heal itself.

Only those succulents that are weak themselves, or those experiencing continuous rainy weather when infected, will be unable to resist mold and develop black rot.

If you have an injured succulent, to be safe, you can spray a small amount of carbendazim on the wound to protect it. Although spraying carbendazim doesn't solve the fundamental problem, it can form a protective film-like layer on the wound surface. When hyphae or spores land on the wound, they will be killed by the residual carbendazim.

But regardless, I still want to emphasize that mold reproduces extremely fast. In the face of these lower plants, the best strategy is not to give mold an environment to reproduce.

The growing media we use are sterile. Not only that, but even when thoroughly watered, properly mixed growing media doesn't easily grow mold. The reason is that mold, in a warm and humid environment, also needs nutrients from the succulent to reproduce in large numbers. And these growing media are not suitable for mold growth. Regular sun exposure and keeping succulents in their optimal growing state is the best way to resist mold infection diseases.

Beautiful photo appreciation ~ Blue Angel: