Rhizoctonia: symptoms and treatment of this parasitic fungus

Rhizoctonia is a fungal disease

Image – Flickr / Scot Nelson

Plants, and particularly tender plants such as seedlings or very young ones, can be affected by fungi. They, which are neither plants nor animals, but constitute a kingdom of their own, called Fungi, usually survive by feeding on decomposing organic matter, but there are some that are parasites, such as those of the genus Rhizoctonia.

Rhizoctonia are, along with Pythium and Phytopthora, the fungi that cause the most plant diseases. Because, it is important to know them to know what to do to control them.

Origin and characteristics of Rhizoctonia

The rhizoctonia hyphae are whiteRhizoctonia hyphae are white.

Image – Wikimedia / Tashkoskip

One of the problems with this fungus is that it is found all over the world, and it uses many plants as its host. But that can benefit us, because even if I write from Spain and give you advice to treat them in this country, it is more than likely that what I tell you will help you even if you are in China or anywhere else.

So with that being said, let’s talk about its features. As it does not produce spores, It can only be recognized by the mycelium; that is, that set of hyphae that humans later see as “dust”, which is white to dark brown.. They live on the ground, and like all fungi, high humidity stimulates their growth. The most common species is the Rhizoctonia solaniwhich affects both ornamental plants (including grass) and garden plants.

What are the symptoms and damage it causes?

As it is a soil fungus, the parts that will be affected first will be the roots and then the stem. The vast majority of plants, once they are without roots, die, and the worst thing is that from the time the infection occurs until we realize it (that is, until the stems show badly) a time passes. Because of this, it is often very difficult to detect the problem, and even more so to take measures that could otherwise help to control it.

In addition, the symptoms and damage it causes are:

  • Roots turn brown and then black, rendering them useless. If the plant has tubers, we will see brown cankers.
  • The stem turns brown as well, and may ‘thin’ and / or have slightly sunken brown cankers.
  • Leaf and / or fruit drop.
  • Their growth slows down more and more.
  • In severe cases, the plant dies.

Is there an effective treatment for Rhizoctonia?

Rhizoctonia is a serious diseaseRhizoctonia is a serious disease

Image – Wikimedia Commons / Ninjatacoshell

I’m going to be honest with you: the answer is no. There is no product that can help you cure the plant and eliminate the fungus, not 100%. What do exist are products that help prevent and control the disease (in its early days). Also, there are a series of measures you can take so that your crops are not affected (or at least, to minimize the risk of infection as much as possible).

But before talking about it, let’s see what to do if we have or suspect that we have a plant with Rhizoctonia:

What to do if I have a potted plant with Rhizoctonia?

The first is pick it up and keep it away from other potted plants to avoid infection. You must take it to a bright place, but where there are no strong drafts.

Next, you have to extract it from the pot and wrap the root ball with absorbent paper. In this way, it will lose moisture, which is just what the fungus needs to survive. The next day, plant it in a new pot and treat it with systemic fungicidelike the Moncut. And to wait.

Note: if the affected plant is a cactus or succulent, remove all the soil and wash its roots with water and a little diluted fungicide. Cut out those that are black with clean and disinfected scissors, and then plant them in a new pot with a pumice or similar.

What to do if I have a plant in the garden with Rhizoctonia?

When it is a plant in the garden that is sick, the situation is complicated. Therefore, I recommend you make a tree grate, for example with earth, and treat it with systemic fungicide (on sale here!). But instead of spraying the plant, Pour the dose indicated on the container into the irrigation water, and then water the landaround the stem so that the roots are well soaked.

If it is a herbaceous (zinnia, cyclamen, etc.), unfortunately the best thing to do is to tear it off and burn it. Also, it is important to treat the area where it has been growingwith fungicide.

Preventive measures against Rhizoctonia

The rose bush may have rhizoctonia

The rose bush can have rhizoctonia

Although you probably do not believe, this is a fungus that can do a lot of damage but that can be kept at bay quite easily. We can’t stop him from being on earth, but we can stop him from acting. And how? Well, keeping this in mind at all times:

It only affects weak plants.

Basically this means that It is very difficult for a plant that is well hydrated, fertilized, in a place where it can grow without difficulty, and where the climate favors its development, to be affected by the fungus.

Therefore, the preventive measures are:

  • Bet on native plants. They adapt without problems to the climate and conditions of your area, so they can be healthy from day one.
  • If you prefer exotic plants, choose those that know that they will live well in the place where you want to put them. Look to see what their resistance to cold is, if they are sunny or shady, if they prefer acid soils o clayey,… All this is important to know, since it is the difference between having a low-maintenance garden (or patio), to a high-maintenance one.
  • Know the needs of your plant. Water it, fertilize it and transplant it every time it needs it.
  • Do you like to sow seeds? Uses substrates (such as this) that drain the water quickly, and top them with powdered copper what can you buy here! (If it is summer, use a better spray fungicide so as not to burn them). Maintain the treatment at least until the seedlings take 2-3 pairs of true leaves, although I advise that it be prolonged until the second year of life if they are trees and palms.
  • Treat cuttings with fungicide too. This way you avoid taking unnecessary risks. Mixing the copper with the substrate will suffice. Repeat the treatment once every 15 days.
  • Do not use substrates that have already been usedas it could contain remains of Rhizoctonia and infect the plant you want to put there.
  • The pots that had diseased plants have to be washed thoroughly with hot water and dishwasher. Then dry them in the sun.

We hope that with these tips your plants do not have to worry too much about Rhizoctonia.

Rhizoctonia: symptoms and treatment of this parasitic fungus

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