A Detailed Guide to the Symptoms, Causes and Treatment of Black Rot in Succulents
Black rot mostly occurs in summer. Right now, many friends' succulents have already started showing black rot. What exactly are the symptoms of black rot, and what causes it? If you want to make it through the scorching summer, how should you carry out treatment? Take a look at the information we've put together for you!
1. Symptoms of black rot
As the name suggests, when a succulent gets black rot, its leaves turn black and rot away just like in the picture.
2. Causes of black rot in succulents
First of all, everyone needs to understand why black rot happens. Many succulent growers think water is the main cause of black rot. Actually, that is not the case. Water is indeed one of the important causes of black rot, but it is not the absolute cause. Black rot happens because there are harmful bacteria in the soil or grit that are harmful to plants, and under high temperature and high humidity they begin to multiply in large numbers, which is what causes the plant to rot.
Some people compare black rot to cancer: treat it early, amputate in the middle stage, and in the late stage just eat and drink well. Actually, it is more like a plague. Cancer takes time to develop, whereas black rot, when the conditions are right, can rot everything through in a single day. Black rot in succulents is caused by the fungus “Fusarium oxysporum” (the pathogenic fungi of black rot are not necessarily the same for different plants). Fusarium oxysporum is a type of facultative parasitic fungus that can both infect plants and survive in soil. Like other plant pathogens, it shows infraspecific differentiation and can infect many plant hosts. It is not unique to succulents; in fact, the wilt diseases of more than 100 kinds of plants, including cucurbits, Solanaceae, bananas, cotton, legumes and ornamental flowers, are related to it. A search online will reveal that Fusarium oxysporum has even caused an extinction crisis for bananas!
3. Ways to prevent black rot in succulents
(1) You can spray carbendazim and similar chemicals a few times just before summer arrives, to reduce the harmful bacteria in the soil.
(2) Put more grit in the soil so that there is more fresh air in the pot (harmful bacteria are generally anaerobic)
(3) Place them in a ventilated spot as much as possible; if there isn't one, you can use an electric fan instead.
(4) When dry, let it dry out completely; when watering, water it thoroughly. This degree of dryness needs to be controlled well; you can let it stay dry for four or five days, but it is best not to let it go too long, otherwise the roots will suffer. For watering, I like to use a nozzle and water heavily, and water for a bit longer, because clean water can also wash away some harmful substances with it. After watering, do not expose them to strong sun right away; it is best to let them sit in the shade with ventilation for a day. This keeps the water in the soil from being too damp.