The three main pathogens.
Fungi : these are the important ones in Cactus and in the other Crassas plants.
Bacteria: ever occurs in Crasas.
Viruses: in Crasas are very rare and difficult to determine by visual symptoms.
There are many species of fungi that attack Succulents.
The typical damage is rottenness, both in the stems, as in the neck at ground level or in roots.
The Cacti in particular sometimes have rots starting at the stem end rots and whole plant.
Diseases should not be talked about in all cases, and many of the ills that can afflict them come from bad cultivation practices.
We will see it through the symptoms that arise.
The stem of the plant is rotten.
It is a clear symptom that there has been an excess of irrigation.
Therefore, if there is already a clear rot, there is no remedy.
If you have healthy stems, proceed to remove the plant from the pot completely.
Clean it of dirty parts or that present indications of rotting and remove the earth and let dry, aerating it conveniently.
Remove dead or damaged roots with clean scissors and cut straight and clean.
As a precaution apply a fungicide to the none affected part of the cactus and transplant it to another dry and clean pot .
Let it stand for 15 days before re-watering with caution.
The plant loses its green color and they are dry or hallow inside.
This is a case contrary to the previous one. In other words, there is a clear lack of irrigation here.
The plant is thirsty.
If it is summer, we have neglected it and the plant is exhausted and pulls its reserves in the succulent leaves and if it is winter, some water is needed.
Therefore, submerge the plant in water, let it absorb water and control the waterings so that it does not dry out.
Green color loss on succulents ,we could find some case of Chlorosis , which is the lack of iron in the substrate, for different reasons.
Fusariosis – Fusarium fungus
The fungus Fusarium oxysporum, which lives in the soil, infects the roots due to excess moisture.
In the event that the alteration affects only the lower part, the rest can be saved by cutting it clean and using it as a cutting, to start it over again.
The species that causes most damage is Fusarium oxysporum, which is subdivided into numerous forms and each of them is a specific parasite of a certain plant.
Thus, for example, Fusarium oxysporum f. sp. dianthi, is the specific form that attacks the carnation.
As for Verticillium, the species that cause the most damage are V. alboatrum and V. dahliae. It is a soil fungus, which causes the vascular disease called, Verticilosis.
Temperatures between 21 and 24ºC, as well as high temperatures, favor the development of this disease. The attacks of Fusarium and Verticillium begin in the roots, by which they enter the plant.
Fusarium oxysporum causes necrosis in these roots, whereas Verticillium does not.
The Verticillium is a fungus that attacks the roots of the tree and that, later and progressively, goes up the stem. Then it reaches the branches and causes the obstruction of the sap conducting channels, which causes a necrosis on certain parts of the plant.
For this reason the attacks of Verticillium are less dangerous, being able some plants to recover, if they change the conditions that favor the development of the fungus.
From the roots, the fungi pass to the conducting vessels of the sap, which are obstructed, making it difficult to circulate it.
The causative agents of this disease are Phytopbthora, Pythium, Rhizoctonia and Thielaviopsis, as well as fungi of the genera Sclerotinia and Fusarium.
The symptoms of these diseases are:
It is presented in seedlings and cuttings. The fungi attack from the ground to the root and base of the stems.
The neck and the root darken, wither and rot. The little plants die quickly.
Some of the most commonly affected ornamental plants are shrubs such as, Chamaecyparis Pittosporum, Poinsettia (Euphorbia), Hibiscus Rhododendron; or fat plants like Aloe, Cactus …
Rot of the neck
The causative fungus is Phytophthora. At the base of the stems a brown or blackish discoloration is observed. The attacked parts rot.
The development of the fungus, like Fusarium, is favored by excessive irrigation.
As a prevention, it avoids waterlogging and destroys diseased plants.
Several fungi can cause this deadly disease: Monosporium, Phoma, Sporotrichum and others.
As a precaution, avoid injuries or wounds to prevent the infection of these fungi and bacteria.
The fungus Phoma spp. in Yuca.
Gray mold (Botrytis)
The fungus Botrytis cinerea causes rot and manifests as a characteristic gray or brown mold on leaves, flowers or stems. Later these areas attacked by the mold, are covered by a thin layer of whitish grayish mold.
After a hail or heavy rain injuries occur where the fungus enters.
It mainly attacks younger plants and those that are weaker or sicker. This fungus has the ability to enter the plant tissue of the plant in question, which causes death.
When the plant is affected, it takes a brownish color and on this area the fungus develops, with a grayish coloration, an area where the fungus Botrytis multiplies and propagates.
As a necessary condition, we must have the plant with good aeration, avoiding moisture, as this favors the growth of the fungus.
To prevent it, the next day applies an antibiotic antifungal, for example Captan, in order to protect these wounds.
It is caused by Botrytis cinerea, which is the conical form of Sclerotinia fuckeliana.
We can detect it if we find symptoms like:
Gray mold of leaves, stems, flower buds and flowers, which can deteriorate completely.
To control these diseases, we recommend;
Treatments with diclozolinato, glicofeno or vinclozolina, that have preventive and curative effect. It is also possible to use polyvalent fungicides or antibiotics such as benomyl, methylthiophanate, polyoxin-B and procymidone.
In preventive treatments can be used captan, diclofluanide or folpet.
When it is necessary to repeat the treatments several times, as it can happen in the cultivation of flowers and ornamental plants in the greenhouse, it is convenient to change the product or combine two of them.
In this way, it is possible to avoid problems of resistance of fungi to fungicides.
Speckled and dry spots
They are caused by various fungi such as Ascochyta, Phyllosticta, Perisporium, Macrophoma, etc.
As soon as the first spots are observed, the propagation can be contained by spraying with fungicides indicated for Botrytis.
The fungus Uromyces produces blisters and pustules (hoaxes like the head of a pin).
The symptoms presented by the plants affected by the fungus Uromyces, are light brown pustules, even dark brown. The areas attacked, die.
It is caused by rusts, which are the organs that carry the spores of the fungus. This fungus develops in the cell tissue of the plant, so that the fungi extract the nutrients from the cells, killing the plant.
If the attack of the Rust is very powerful and generalized, the plant can be considered dead.
To combat it we can apply it, for example Eurapen. We must apply it in a powdered form, on the underside or bottom of the leaves.
If you can also eliminate the leaves or dead zones, preventing it from spreading throughout the plant.
Mildew presents the symptom of being a gray fluff, on the underside of the leaves. In the upper part of the leaf, they will look like yellowish spots, which will darken with the passage of time, if we do not treat them.
The Mildew, can also attack the stems of the plants and if it is a powerful attack, it can kill the plant.
The culprit is the fungus Mildew, which develops inside the plant and is seen externally as a fuzz in the affected areas. The humidity environment, promotes the development of the fungus.
To control it, it can be applied, for example Euparen in pulverized form and as a prevention. If you can, clean up the areas attacked.
The symptoms of this fungus are like a whitish and sticky powder, which covers the leaves and stems. It causes the plant to present deformations and if the attack is strong it discolours them with a brownish color and kills the plant.
Oidium is caused by a fungus that takes advantage of the presence of nitrogen in the fertilizer, by the variation of temperatures and by a high planting density.
The powdery mildew attacks mainly the younger and more tender tissues, so the plant is more sensitive at the time of sprouting and that is when it is necessary to be more careful.
It spreads better with warm temperatures, even without high humidity.
They can be treated, also with Imugan especially or also with Euparen.
The Erwinia bacteria can infect wounds or injuries and cause black rot.
The internal tissues are softened and decomposed. The infection promotes excessive humidity and cold (frost cracks).
It has no cure with chemical products and the only thing that could be done is to eliminate the plant to prevent it from spreading to other specimens.
Black rot can also be caused by the fungus Helminthosporium. Against this is recommended Captan.
In summary, in order of importance and where they affect, mushrooms are (very rare name):
Fusarium (root) – Rhizoctonia (root) – Cephalosporium (aerial zone) – Cylindrocarpon (root) – Alternaria – Sclerotium (root) – Phytophtora (root) – Helminthosporium (aerial zone) – Pythium (root) – Microconidia (aerial zone) – Macroconidia (aerial zone) – Thielaviopsis (aerial zone) – Trichoderma (root) – Aspergillius (root) – Cladosporium – Ulocladium – Acremonium – Stemphyllium (aerial zone) – Verticillium (root) – Conothyrium (aerial zone) – Phyllosticta (aerial zone) – Gloesporium (aerial area).
Chlorosis is the yellowing of the leaves, for lack of chlorophyll.
Ferric chlorosis manifests, by the absence of the nutrient, iron. It can also be given by the lack of manganese or zinc in the plant.
To distinguish which metal is involved, if the iron chlorosis begins with the younger leaves or terminal buds, it will be a lack of iron.
If, on the contrary, the Chlorosis occurs in the internal or older leaves and from the outside, it will be absence of manganese and zinc.
Iron is essential to produce chlorophyll, which gives green color to the leaves of plants. For this and that the roots absorb it from the substrate, it must have a pH between 5.0 and 6.5, this is slightly acid pH.
Iron chlorosis can cause total defoliation.
Factors that can cause Clorosis.
We can cite exhaustively some of the causes that can cause ferric chlorosis in our plants. They do not have to give all of them and less at the same time.
- Substrates or alkaline soils (pH> 7)
- Environmental pollution due to the presence of CO2
- Insufficient drainage
- Problems of absorption of nutrients: roots damaged and / or compacted or even underdeveloped
- Nutritional defenses of the plant, poor or alkaline soil
- Little mobility of iron, due to the presence of high levels of manganese, zinc, copper, nickel, cobalt, which prevent the absorption of iron.
- Soils or substrates too clayey or flooded
- Extreme temperatures or excess light, in some cases
Effects of Clorosis
The effects can be the following:
- Necrosis of the leaves
- Defoliation of the plant
- Reduction of shoot size
- Smaller fruits
The solution will be to apply fertilizers rich in iron chelates, correcting the yellowing of the leaves, etc., which can be found in specialized stores.
Depending on the effects that Chlorosis produces on our plants, we will act on them.
How to control fungi.
Preventive measures, in the case of fungi that affect the roots.
- Well-drained substrate
- Keep substrate dry in winter
- Substrate well disinfected, with steam or chemical to the effect (oxyquinoline, propanecarb, etc.)
- Before planting, wet the roots with some fungicide in aqueous solution (fenaminosulf, propanocarb, sulf, oxyquinoline, etc.)
- Avoid waterlogged substrates
- Fertilization rich in phosphorus and more in potassium.
- The cactus should be in an airy and illuminated place, this last one especially in winter
Preventive measures, in the case of fungi that affect the aerial zone:
- Decrease environmental humidity and treat with fungicide, spraying on the surface of the plant.
- Use fungicides such as copper, methylthiophanate, benomyl, dicyclidine, etc.