Cryptogamic diseases : what are they ? How to protect yourself from them ?

In the vegetable garden as in the orchard, cryptogamic diseases can lead to significant yield loss, and they are just as devastating in the ornamental garden. Moreover, they are responsible for almost 8 out of 10 problems faced by gardeners. It is therefore essential to learn to differentiate them in order to apply the appropriate treatments. But we can also prevent their occurrence to protect their crops. Let’s shine a spotlight on the main cryptogamic or fungal diseases in the garden, their symptoms, possible treatments and ways to fight against their appearance.

What is a cryptogamic or fungal disease?

It is a disease caused by a filamentous mycelium on which develops a pathogenic fungus. It is unquestionably the most important scourge for plants of any type whatsoever.

The main fungal diseases that can be faced are:

  • The damping off: Newly planted plants die slowly after losing their leaves and becoming gray and soft due to the rot that hits them hard. This leads to a sometimes considerable loss for gardeners. This fungal disease is extremely contagious.
  • The peach leaf curl: it is due to the parasitic fungus Taphrina deformans The disease causes the blistering of young leaves which, in addition, turn reddish or may also become discolored. It also impacts the apricot tree, the nectarine tree and affects not only the foliage but the fruits. If nothing is done, the fruit shrub is doomed to certain death since it ends up losing all its leaves, which obviously makes photosynthesis impossible.
  • The rust: very common, it causes concentric spots on the foliage, white or brownish, but only on the face. On the other hand, on the underside of the leaves you can see a kind of down that the wind blows at the slightest breath so that the rust quickly contaminates other plants in the garden. If left untreated, this fungal disease can cause plant death.
  • L’aternariose: two pathogenic fungi are to blame, namely Ulocladium et Alernia. When the fungal disease is declared, the tubers rot, the foliage turns brown.
  • The fumagine: it causes the blackish or grayish felting of the foliage, at least on the visible side of the leaves, so that the plant can no longer absorb the light. It becomes weak and produces less.
  • The botrytis: this cryptogamic disease is frequently called gray rot. Its responsible is the fungus Botrytis cinerea, a parasite that makes no distinction between different parts of plants (leaves, stems, roots, flowers, fruits). Thick greyish felting, white or brown blisters, necrosis, are the symptoms that should alert. Very contagious, botrytis can ruin an entire vegetable garden.
  • The mildew : in the medium term, it leads to the curling of the foliage and its reddening, then the fall of the leaves. Without treatment, plants affected by downy mildew see their green wood wither, and they eventually die.
  • apical necrosis: it is due to poor assimilation of calcium, and can be detected by the black spots on vegetables and fruit vegetables. The alternation of humidity and dryness favors this fungal disease.
  • The tavelure: another cryptogamic disease feared by gardeners who mainly own an orchard. It causes great damage to pear trees, apple trees… It is also the first enemy arborists. It is recognizable by the dark, velvet-like spots on the upper surface of the leaves which eventually fall off and by the drying of the flowers of fruit trees. The fruits are just as affected by scab since they can present black spots, cracks or even deformations. Fruit trees are weakened and, as a result, fruit production is drastically reduced.
  • L’powdery mildew: it can be identified by the white felting visible on the surface of the leaves which are likely to deform. Fruit trees and cucurbits are very susceptible to powdery mildew, but unfortunately they are not the only ones, and powdery mildew considerably reduces production. However, it is not a fatal fungal disease for plants.
  • L’anthracnose: it is favored by certain climatic conditions, namely an ambient temperature of the order of 20 to 22°C associated with excessive humidity. Cucumber and melon are very sensitive to it. It manifests itself by brownish spots on the foliage, and on the fruits hollow spots of concentric shape which turn from brown to pink.
  • The necklace: twig dieback, foliage drying out are the main signs. Diseased fruits can quickly contaminate others when they are all in contact.

If in doubt, do not hesitate to seek advice from a gardening professional.

How to treat a fungal or cryptogamic disease?

For this type of disease to develop, all it takes is one confined, hot and humid environment. These are conditions that favor the occurrence of parasitic fungi. We also know that watering in spurts, too abundant and not very regular, is likely to be the cause of this type of disease in the garden.

There are pesticides to treat plants affected by a cryptogamic disease. Those are fungicides and they fall under the category of pesticides.

It is essential to use a perfectly appropriate treatment product to obtain good results. A fungicide may be able toinhibit the growth of a pathogenic fungus but also of destroy it if it acts on the metabolic activity vital to the development of the fungus responsible for the disease. There are chemical fungicides and natural fungicides. In addition, they have different mechanisms of action.

Here are some things to distinguish surface fungicides from systemic versions. Inquiring well before purchase helps to avoid confusion, processing errors, but you must also scrupulously respect the mode and conditions of use indicated on the packaging.

Surface fungicides

Based on sulfur products or even copper, the contact fungicides which should be used with great moderation because they are toxic for humans and for plants, they are effective even though the treated plant does not absorb them. This type of product is quickly washed away by rain and watering. Also, it has no action on the leaves that appear after its application.

It is greatly preferable to reserve them only for a preventive use rather than curative in order to limit their impact on human health and the environment.

Systemic fungicides

These are so-called fungicides penetrating since the plant absorbs them. This type of product can be translaminar (we also say local), with upward diffusion or even with total diffusion, that is to say downward and upward.

Systemic fungicides in the first two categories penetrate the foliar system upon application. They are therefore not washed away by rain or irrigation water. However, they do not protect future leaves because once absorbed they move little in the plant. On the contrarythose at total spread which can be applied to the foliar system but also to the soil, they are consequently absorbed by the roots, do not undergo leaching and even protect the leaves that develop later.

Systemic fungicides are used instead curative pull because they act on the development of pathogenic fungi already present and responsible for cryptogamic diseases.

What about natural antifungals to treat your plants?

It is sometimes better to opt for a herbal decoction in order to care for plants affected by a cryptogamic disease or even to limit the risks by playing the card of prevention.

Be careful, however, not to treat at random, thinking that natural solutions are harmless. It is of course false. Any treatment should always be applied wiselyon a case-by-case basis, at the right time, and the same goes for preventive solutions.

For information, among the natural solutions against fungal diseases in the vegetable garden, orchard and pleasure garden, we mainly find:

  • Milk,
  • Le bicarbonate de sodium,
  • Sulfur,
  • nettle manure,
  • dandelion manure,
  • Le purin d’absinthe,
  • Horsetail decoction,
  • Garlic decoction.

These are natural antifungals that have proven themselves provided they are used at the right time, on certain types of plants, knowing also that we must respect the right dosages.

How to protect your plants against cryptogamic diseases?

Even if we are reluctant to use treatment products that do not have a very good press because of their impact on health and the environment, we can only recognize their efficiency when they are well used and applied. at the right time. However, it is possible to protect crops against fungal diseases by adopting certain gardening rules.

Promoting prevention avoids having to resort to fungicides. In the garden, we can quite take inspiration from agronomic practices even if, let’s face it, they are sometimes complex to implement. It is still worth adopting them.

  • Choose, whenever possible, varieties more resistant to cryptogamic diseases,
  • Opt for crop rotation,
  • Limit early sowing because some fungal diseases are influenced by the sowing date,
  • Prohibit excessive use of fungicides,
  • Space the plants well to avoid confinement because for the good health of the plants, the air must be able to circulate in the heart of the branches and between the leaves,
  • Do not plant too close to a wall, allow at least 40 cm between the plant and the low wall,
  • Preferably use new potting soil when sowing, transplanting or planting,
  • Enrich the soil with mature compost if the fruits and/or vegetables do not assimilate calcium well,
  • Limit the inputs of nitrogen-rich fertilizers because they promote fungal diseases,
  • Beware of excess humidity or even irregular watering which increases the risk of development of pathogenic fungi,
  • Ensure that the fruits are not in contact with the ground, by installing mulch or stakes depending on the case, but also that they touch each other as little as possible,
  • If plants are affected by a cryptogamic disease, it is essential to eliminate all affected parts and then burn them to avoid any risk of propagation. It goes without saying that the plant parts eliminated must in no case be integrated into the compost.

Sure, fungal diseases cannot be avoided 100% in the garden. It is therefore advisable to observe its plantations regularly in order to detect the slightest symptom suggesting the presence of pathogenic fungi. This allows you to react quickly. Good observation is also essential to make an accurate diagnosis and thus be able to apply the treatment method that is best suited.

Finally, note that cryptogamic diseases alone deserve a real encyclopedia. They affect indoor plants, plants in private gardens, agricultural crops and are the subject of scientific studies.

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