Rhizoctonia solani (Rhizoctonia solani) is a soil-borne fungus that attacks many plants, including vegetables, cereals and ornamentals. It mainly attacks underground organs and causes diseases such as root, stem and crown rot, as well as damping-off. Let’s find out together how to identify this fungus, the crops affected, and above all, how to protect yourself from it using effective natural solutions.
What is Rhizoctonia solani?
Rhizoctonia solani fungus is a soil fungus widely distributed in France, Europe and around the world.
It is a fungal disease that mainly attacks the underground organs of plants . Present in different climates, this fungus develops particularly in humid areas where conditions are favorable for its proliferation.
Rhizoctonia solani is a dreaded enemy of potato crops , but it also affects many other cultivated plants as we will highlight later.
In a garden or field, the presence of this fungus can lead to a significant reduction in yields , impacting the quality of harvests, particularly in the case of potatoes, where the tubers can be severely damaged.
Which plants are affected?
Rhizoctonia solani affects several families of plants, including Solanaceae (potato, eggplant, tomato, etc.), Cucurbitaceae (melon, zucchini, cucumber, etc.), Brassicaceae , Umbelliferae , Malvaceae and even certain cereals such as corn.
We also find it on beet crops .
Sensitive vegetables include carrots, radishes, beets, lettuce and beans.
Mushroom biology
Rhizoctonia solani can overwinter and persist for several years in the soil in two main forms: mycelium and sclerotia. The latter are compact and resistant structures, composed of fungal filaments, which allow it to survive in organic matter and plant debris present in the soil. Once in place, it can remain latent until environmental conditions are favorable for its development.
In spring , when temperatures rise and humidity sets in, the sclerotia germinate and produce mycelium, a network of filaments that extends into the soil. This mycelium is capable of rapidly infecting underground plant organs such as tubers, stolons, roots, or sprouts. Infection occurs by direct penetration of tissues via the plant cuticle, often through small wounds that facilitate the entry of the fungus.
Once established in the plant tissues, Rhizoctonia solani develops and produces a network of mycelium, gradually invading the roots and underground parts of the plant. The fungus also reproduces by forming sclerotia and basidiospores. The latter are easily spread by wind, or via contaminated tools, thus increasing the spread of the infection from one crop to another.
What are the favorable conditions for Rhizoctonia solani?
Here are the main situations in which this fungus thrives:
- A cool, humid climate after planting.
- Planting too early in cold, poorly drained soil
- A form of soil moisture
- A long delay between topping and harvesting, which increases the risk of contamination by sclerotia.
- Crop rotations too short
What are the symptoms of Rhizoctonia solani?
Here are the main damages caused by this disease:
Symptoms in vegetation
Rhizoctonia solani affects plants as soon as they emerge , at the level of underground and aerial organs. The first observable sign is often the presence of brown filaments and rot that extend around the roots and stems.
When infection begins early, plant emergence is irregular or delayed . Young shoots are particularly vulnerable and quickly show corky necrosis on their tissues. This can cause general weakening of the seedlings and, in the most severe cases, prevent complete emergence of the plants.
In later attacks, several symptoms appear on the aerial parts of the plants . Stems may begin to curl, while leaves take on a purplish tint at their edges. Yellowing or drying of the foliage often follows this discoloration.
In wet weather, another indicator is the appearance of whitish mycelium at the base of the stems.
Symptoms on tubers
Potato tubers affected by Rhizoctonia solani show cuts and cracks on their surface. A corky appearance is observed on the skin of the potatoes.
Infected tubers become deformed and have black sclerotia on the surface. These sclerotia are very resistant and do not disappear when washed. Their presence affects the visual appearance of the potatoes, but also their conservation.
Furthermore, brown corky plugs a few millimetres in diameter can form at the lenticels of the tubers, without this progressing inside the flesh.
Economic impact on crops
For professionals, the economic consequences of Rhizoctonia solani can be considerable. On potatoes, it causes yield reductions and a depreciation of the harvest due to the presence of sclerotia. A severe infection makes the tubers unsaleable, which leads to significant financial losses.
What solutions are there against Rhizoctonia solani?
Protecting your crops against Rhizoctonia solani fungus requires vigilance and the implementation of suitable cultural practices:
- Favor long crop rotations on uncontaminated land in order to reduce the presence of the fungus in the soil.
- Use healthy, certified plants to avoid introducing disease into your crops.
- Plant in warm, well-drained soil to encourage rapid, healthy emergence of seedlings.
- Reduce the time between topping and harvesting to limit the formation of sclerotia.
- Clean the soil regularly , removing healthy or diseased plant debris and weeds, to prevent the survival and spread of the fungus.
Agrobiotop solutions against Rhizoctonia solani
As an expert in agrobiology, we have developed soil improvers that effectively combat brown Rhizoctonia:
We also recommend the following solutions to protect your plants:
