With the beginning of autumn almost all succulent and cacti begin to prepare for the vegetative stasis which will last until February/March. In the winter months, cacti (with some exceptions such as Melocactus, Discocactus and epiphytes such as Epiphyllum) and many succulents (with the exception of those originating from the southern hemisphere or areas such as Madagascar) stop growth and go dormant to recover energies and be able to flourish during the following season. In these months the plants should be kept cold and should not be watered. However, it is useful to carry out some preventive treatments to prevent the formation of mold or fungi during these months, thanks to the winter humidity, which, when the temperature start to rise, triggers rot. Warning: preventive treatments with chemical products can be useful but do not necessarily have to be carried out. It is simply a preventive measure, since the best form of defense is always the spartan cultivation of plants accompanied by a good exchange of air during autumn and winter. There are growers who limit these treatments to the essentials, perhaps favoring products with a low environmental impact (I myself have adopted this decision for years) and growers who abuse chemical products in the hope of thus making their plants invulnerable to animal parasites, fungi and mold.

In this article, which completes what has already been explained in other articles (which you will find thanks to the internal links) we see what is advisable to do in these weeks to protect the plants and limit losses due to rot or parasites as much as possible. (…)

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L'articolo Here comes autumn: what treatments can we do to protect succulents and reduce losses? proviene da Il fiore tra le spine.

We see them in detail in the following article (…).

Premise

By the time of June, two first dangers for succulent plants should have passed by now, if we have done everything correctly (and regardless of the fact that this spring has been quite anomalous). I am referring to the danger of cracks on the cacti stems and that of burns following a late or “hasty” exposure. Once the cacti have resumed vegetating after the winter stasis, in fact, it may happen that following the first waterings (if too abundant or too close together) the stem “splits”. In this period of the year, even in the case of a wet and cold spring like the latter, cacti and succulents should have already received at least two or three waterings and the stems of the plants should have swollen. If the recovery has taken place gradually and the plants have returned swollen, the risk of stem splitting for this year can be said to have been archived.

In some ways similar speech in terms of exposure: to date all the plants should have been in their ideal location for some time now, where they will remain until autumn. In other words, those who kept cacti and succulents in the basement, entrance halls or garages should have moved the plants to full light (or half light depending on the genre) by now, under penalty of etiolation. Abruptly moving the plants now, with the June sun starting to get stronger, can expose the plants to the risk of severe burns on the stems. Whether the spring is cool or not, whether it is humid or not, the plants must be gradually accustomed to intense sun or direct sun and this must be done between the end of March and the beginning of April. In this way cacti and succulents are able to get used to direct sunlight very gradually, strengthening the epidermis well before the summer sun hits them. If you haven’t moved your plants yet, do it immediately but repair them with shading nets (especially during the hottest hours of the day), otherwise the first burns will begin to appear in the coming weeks!

Maximum air

Having exhausted the necessary premises, which are nothing if not common practices in the correct cultivation of cacti and succulents in general, we recall that the main element of cultivation, at this point, is trivially… the air. Trivially, because this element is often underestimated, or even not considered at all, taking it for granted. The air, on the other hand, is the main factor for the healthy growth of any plant and in this season, with temperatures starting to rise significantly (on sunny days in a completely open greenhouse it can easily exceed 40 degrees Celsius already in June, let alone August), the plants need as much air circulation as possible.

Anyone who cultivates in a very large professional greenhouse will have to open the structure as much as possible, raising the side curtains and possibly leaving the front and rear doors open. Those who cultivate on balconies and terraces should have no problems whatsoever, while those who cultivate in those small greenhouses covered with a transparent cloth must do nothing but… get rid of the greenhouses, remove all the plants from there and disassemble the greenhouses, which can return comfortable, at best, in winter (although they are still not the best due to the limited air circulation they allow). In this period, if we keep the plants in this type of structure, even by raising the openings in the transparent sheet to the maximum, we will still not be able to ensure the plants the air they need, and with high temperatures and humidity the risk of “boiling” plants or creating the ideal environment for the formation of molds and fungi is very high. Therefore, if you haven’t already done so, remove the greenhouses (which can be simply used as shelves) and, since the plants will not be sufficiently accustomed to the intense sun, shield them with a not too light shading net.

The importance of air and light for succulents plants.

Watering and aestivation

In this period, even if the temperatures are not yet very high this year, it is advisable to increase the frequency of irrigation. If the days are sunny and the weather does not predict rain for the following days, it can be watered once a week. The pace can also be increased to two waterings per week for some species or succulent leafy plants if slight wrinkling is noted. As always, the basic rule is to water only when the substrate appears dry and, if in doubt, postpone it. Beware of the hot months, i.e. July and August, when the difference between the maximum and minimum night-time temperatures is minimal: in conditions of persistent heat, many cacti and many succulents can go into aestivation, slowing down or blocking their growth. In these periods it is better not to water at all, since the plants do not absorb water and the soil would remain moist for too long, with the risk of root rot being triggered.
A few more waterings will have to be reserved for very young plants and seedlings, which are not yet able to tolerate long periods of drought in hot conditions and, at the same time, “push” more than adult specimens.

On the phenomenon of aestivation you will find a specific article at this link.

Fertilization and treatments

In June it is still possible to fertilize succulents. A fertilization is enough, assuming that a first fertilization was given in May or April. If the plants have been repotted a few months ago it will not be necessary to add fertilizer to the water, but if we are dealing with specimens that have lived in the same soil for years, an extra fertilization can be useful to replenish the nutrients once present in the substrate. Pay attention to the product (whether it is in powder or liquid form, it matters little), which must be specific for succulent plants and therefore low in nitrogen and rich in phosphorus and potassium, in addition to microelements. During the real summer, that is in the months of July and August, the fertilizations must instead be suspended.

As for treatments, for years I have minimized the use of pesticides and I only use copper oxychloride and Neem oil. The first is a fungicide which should be administered by nebulization only in the months in which the plants are not in vegetation (in this period it should therefore be avoided). The second is a natural product, with low environmental impact, against parasites, mites and with a modest fungicidal function. Neem oil can be administered, always by nebulization, even in this period, with the foresight to act only when the sun has gone down or early in the morning, before direct light reaches the plants. Targeted fungicides and insecticides can be used in specific cases, for example in the event of an attack by the cochineal or rot that affects several plants. In these cases it is always important to isolate sick specimens from healthy ones and carry out targeted treatments every two weeks.

Here you will find a detailed article on the main adversities of succulents, with general indications on how to intervene.

Always remember that the best weapon against pests and diseases of succulents is correct cultivation, in particular a spartan cultivation, with lots of light, lots of air, little fertilization and little fertilizing.

To repot or not to repot?

In this case there is no definitive answer: during the summer it is possible to repot. Personally I prefer to avoid – except in cases in which the intervention cannot be deferred as the plant is in evident state of suffering and has probably lost its roots – and to postpone repotting until the end of winter and spring. With new purchases, especially if the plants are in peat, repotting is instead recommended at any time of the year: it is better to stress the plant a little rather than leave it in an unsuitable substrate, running the risk of triggering rot. As always, if you repot and clean or shorten the roots, it is important to leave the flared plant in a shady place for at least ten days before repotting. After repotting, wait another week or two before watering, so as to give the roots time to heal effectively. This precaution is especially important in spring and summer, when the plants are growing and are watered regularly: obviously in winter the problem does not arise, since many succulents and almost all cacti must be kept in dry soil.

Other practices

Otherwise, summer is a relatively quiet time for the cactus and succulent grower. It is sufficient to observe the specimens and understand whether they are slowing down their growth (aestivation) or not and adjust accordingly with watering. Finally, a little maintenance certainly doesn’t hurt: you can cut the now dry floral stems in the case of plants such as Aloe, Echeveria, Crassulaceae, etc., just as it is a good thing to remove the dried flowers of the cacti, which with watering they soak in water and can feed molds and fungi.

Seasonal cures in detail

If you want a complete picture of seasonal care, with everything you need to do in spring, summer, autumn and winter to take care of cacti and succulents in the best possible way, you can consult this summary article.

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Correlated articles

Watering cacti and succulents: when and how
How to repot cacti and succulent plants
Substrates for cacti and succulents
The correct soil: the materials you can use

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L'articolo Towards summer: useful tips for taking care of cacti and succulents and avoiding nasty surprises proviene da Il fiore tra le spine.

In this article, we see what you need to do this month for keeping cacti and succulents in perfect health, even preparing them for winter diminishing the risk of rot and loss. (…)

In August, for several years now, I suspend watering altogether. In the greenhouse, temperatures easily exceed 40 degrees Celsius, and many cacti slow down or stop growing because of the phenomenon known as “estivation”. Many species keep to flower regularly (e.g. Gymnocalycium, Ferocactus and some Mammillaria), but it doesn’t mean that the growth’s rate has not slowed down. That’s why I prefer to avoid watering all my plants, except the leafy succulents, and let them follow their natural rhythms. This prevents the soil from staying wet for too long when the plant is in dormancy, and it causes root or collar rot.

Watering

The last watering of the summer is usually at the end of July for all my cacti, especially for those with particular growth rates, such as Copiapoa and Neoporteria, for which I stop watering even earlier, in mid-June. At the beginning of September, I start watering all my plants again, thinning them throughout the month and watering them every ten days at the most. The actual cessation of watering usually coincides with the beginning of October to give the soil time to dry out totally and for the cacti to reduce their internal water reserves and start preparing for autumn and winter. This is true for adult plants: for seedlings and one or two-year-old plants, I extend the watering period until mid-October, but water sparingly. I pay particular attention to plants of the genus Ariocarpus, which I water until mid-September at the latest. These plants, which have tap roots, are sensitive to humidity and have considerable water reserves, and I have learned that with the climate of Northern Italy, characterized by very wet and often cold winters, it’s suitable to stop watering earlier. The plants are not affected at all and do not deflate until late in the winter. Moreover, they bloom abundantly from mid-autumn to the first half of December.

Fertilizations

In September, as far as fertilizing is concerned, it’s better to give the last coat with a specific product (here is an article dedicated to fertilizers for cacti and succulents). You can have a first watering at the beginning of September with only water and add fertilizer in low dosage at the second watering, after about ten days. Fertilizing in September is helpful for the plants: it gives them the nutrients they need to get stronger before the winter break and helps the blooms when they resume in the spring. I generally limit myself to single fertilization in September, but it is possible to fertilize a couple of times before the watering stops, as long as low doses are used. Again, the situation is slightly different for seedlings and young plants (one or two years old): for these, I add fertilizer during the last watering in October to “push” them a bit and strengthen their growth.

Treatments

September is also the month of preventive treatments against parasites and diseases. Since the plants start to vegetate again, it is not recommended to use copper-based fungicide (which slows down the growth), which should be sprayed instead in the autumn months and only on warm and windy days. Some spray with copper fungicide throughout the winter, once or twice a month to prevent the proliferation of fungi or “rust”, but for several years I limit myself to a couple of passes in October and a couple of passes in February, just before the recovery. In September, however, it’s advisable to add a broad-spectrum fungicide to the water for watering and spraying the plants a couple of times with an acaricide or Neem oil, a preventive measure against aphids, mealybugs and other pests.

Checks

It’s important to carefully check the plants to identify those suffering and isolate them immediately to prevent them from spending the fall and winter months in contact with healthy plants. In this way, you can preclude the risk they may transmit diseases that can spread with the humidity that usually there’s in autumn.

Repotting

Finally, stop repotting. For several years now, I have avoided repotting (except for plants in severe pain) in September when cacti and succulents are vigorously vegetating again and in October and November. While repotting can generally be done almost any time of the year, I prefer not to “disturb” my plants at this time of year to avoid the stress of repotting in the crucial phase of preparation for autumn and winter. On the other hand, repotting can be done without problems when the plants are in stasis, i.e. in late winter or, better yet, towards the end of winter, just before vegetative recovery.

All about the repotting in this section of the site.

Also, by repotting plants before the end of winter, we will be sure that several weeks will pass between repotting and the first watering, thus giving any roots that may have been damaged or cut during repotting plenty of time to heal before wetting the soil.

Plants in outdoor

The plants I keep outside the greenhouse during the growing season finally stay in place, exposed to direct sun and weather, until mid-October if the early fall is not particularly rainy. At that point, I move everything back inside the greenhouse, which I leave open until the end of November. In fact, if the temperatures are not too low, it’s essential to give the plants all the air possible even in autumn and winter, opening the greenhouses for a few hours on the hottest and most ventilated days. This simple expedient very much reduces the risk of onset and spreading of fungal pathologies. The “toughest” plants, such as Ferocactus and Echinocactus, will return to the outside of the greenhouse from the middle of March to help them get used to the direct sun gradually and avoid sunburn.

Succulent plants and summer: everything you need to know.

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L'articolo September is a brilliant month for all cacti, but pay attention to proper care ahead of autumn proviene da Il fiore tra le spine.

Let’s talk about cacti and diseases starting from a simple photo. The plant that inspired this article, and which you see above, is (or rather, was) an Ancistrocactus (=Glandulicactus) mathssonii. I had obtained this specimen with my sowing about ten years ago and fortunately eight or nine other “brothers” of this plant are still in perfect health, growing and flowering regularly. This particular plant, although treated exactly like the other specimens of that sowing and planted in the same type of substrate in which my other mathssonii live (clay, marl and 60% aggregates), a couple of years ago took a fungal pathology and within a few weeks it was dead. I think it was fusarium, but today it doesn’t matter, because the disease has run its course and what remains is… the armor of this cactus, that is a beautiful interweaving of thorns that embraces the void left by the stem which, over time, it dried up until it decomposed and disappeared altogether. The observation of what remains of this plant, which for a couple of years I have kept along a low wall not far from the greenhouse, where I usually move the diseased plants (by diseases, in this case, I mean generically pathogens and parasites) to prevent them from infecting other specimens, led me to some considerations on the cultivation and treatment of plant diseases.

Considerations that I have condensed in the following article an excerpt of which was also published in the British Cactus and Succulent Society newsletter. (…)

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L'articolo Cacti and diseases: stop anxiety, sometimes we can’t help but let Nature take its course proviene da Il fiore tra le spine.

Many cactus and succulent enthusiasts are convinced that the cultivation of these plants necessarily involves the use of chemical products against diseases and parasites. Others consider the use of these products simply as a component of cultivation to be used in certain cases; still others are not too subtle and at the cost of having healthy plants are willing to destroy their lungs, massacre bees and poison the environment. Talking to them is as useful as trying to convince an agoraphobic to take a walk in a desert. But these people, after all, grow for collection and not for love of Nature or a sincere passion for plants. This article, the result of my personal experience and therefore not to be considered as a “lesson” in an absolute sense, may be useful to everyone else. The experience has led me to drastically reduce the use of so-called “phytopharmaceuticals” or “phytosanitary products” (which do not include fertilizers), especially toxic and synthetic ones. I have undertaken this path for some years now for reasons of health protection (mine first and foremost) and the surrounding environment, considering that many pesticides have, among the various side effects, that of killing bees. The issue relating to the death of bees may seem of little importance to the uninformed, but in reality it has enormous importance on a global level from an environmental point of view.

Let’s see in this article how it is possible to reduce the use of pesticides and fungicides, limit ourselves to products with low environmental impact such as Neem oil and copper oxychloride and still have strong and healthy cacti and succulents. (…)

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L'articolo Two useful products for keeping succulents healthy: Neem oil and copper oxychloride proviene da Il fiore tra le spine.

In the following article, we will see in detail what consists of prevention; which are the pests and diseases that can affect cacti and succulents; such as the symptoms of their action on plants, and how to carry out treatment and care in case of problems. (…)

The importance of air recirculation

The keyword for prevention is air. Air, air and more air. Therefore, airing the environments in which we keep our plants and, consequently, keep humidity rates low. Open greenhouses as much as possible throughout the period from spring to autumn, fans for air recirculation, outdoor cultivation, are all important factors to give our plants the right amount of air. Also, of course, to the use of correct substrates, draining and low humidity, plenty of light and the right fertilization regimes (an excess of nitrogen, for example, forces the growth of succulents and makes them weaker in the face of adversities), proper irrigation and, more generally, cleaning (of soil, pots, tools and instruments, etc.).

Check the plants

A good practice consists, first of all, in observing the plants carefully before their purchase, discarding those suffering, clearly attacked by parasites (such as cochineal, easily recognizable by the naked eye) or deformed at the apex due to the attack of some aphids. Once purchased the plant, it is good to flake it and thoroughly clean the roots (especially if the plant is in peat), checking the condition carefully and repot in suitable soil. Another useful trick is to immediately isolate the plant or plants that we observe in distress or on which we detect the presence of mites (for example the red spider, see below) or parasites such as cochineal. Even more important is to isolate from other plants those subject to fungal attacks: the spores can quickly pass from one specimen to another and cause real disasters. All plants, then, must periodically be checked carefully to identify any problems and isolate the affected specimens to treat them with specific products and avoid that fungi and parasites may affect other plants.

Preventive treatments

Preventive treatments can be useful against fungi and parasites, especially in two specific moments: in autumn and just before the beginning of spring. It is at these times of the year, in fact, that the combination of ambient temperature and humidity, in addition to the low activity of the plants, can favour conditions suitable for the proliferation of mites and bacteria. Before the plants go into stasis, at the end of summer/early autumn, two nebulisations at a distance of 15 days from each other with water and copper oxychloride, possibly combined with sulfur, will protect plants from some types of fungi and bacteria during the winter. In the same way, a couple of nebulisations at the beginning of spring, before watering, will contribute to the prevention at a time when temperatures tend to rise and, with them, the humidity rate due to the March/April rains. Against bacteria in the soil and root parasites, it is possible to carry out systemic treatments, i.e. special products mixed with watering water. Even in these cases, a treatment at the end of summer and one in spring, with the first watering, can be useful for preventive purposes. In these cases, it is possible to use systemic fungicides against radical rot (Previcur can be used against collar rot, while Tebuconazole can be used against fusarium and Propamocarb can be used for a wider spectrum defence). If the fusarium has already attacked the plant, it is advisable to throw away everything: plant, pot and earth.

An excellent choice, respectful of the environment and our health, is to focus on products with low environmental impact, like Neem oil, useful against infestations by mites and parasites. Always remember that chemicals, whether pesticides or fungicides, should be treated with great caution, wearing gloves and masks, as they can be harmful to health if inhaled or in contact with skin (in fact the use of many products is regulated by law and for the purchase and use of some of them, specific patents are required). An interesting alternative to chemicals against insects and pests can be to use natural remedies based on garlic and tobacco.

Some treatment, always for preventive purposes, can be done by nebulization or by the systemic way (i.e. through watering, so that the plant absorbs the product, which will go from roots to stem) even during the growing season. However, if the plants are healthy and robust, the treatments at the end of summer and the end of winter will be enough and the plants will become stronger and will be able to face and solve any problems.

Plant parasites

Plants can be attacked by plant parasites or pests. The first group includes fungi, bacteria, viruses and microplasmas. Fungi and bacteria, in particular, proliferate in the soil in conditions of heat and prolonged humidity. These are, probably, the most insidious and difficult adversities to face. This happens mainly because the presence of plant parasites is manifested only through the symptoms of the disease that they cause to the plant. In other words, fungi, viruses and bacteria cannot be seen with the naked eye, but you can see the effect of their harmful action. Unfortunately, when we realise it, it is almost always too late to save the plant.

 Fusarium  – It is the case, for example, of Fusariosis, caused by Fusarium oxysporum, a fungus present in the soil that causes withering, dry rot and the rapid decay of the plant, which first slows down the vegetation and then stains and then literally withers and dies. In the acute form, the Fusarium causes the basal rot of the affected subject, while in the slow form it causes a chronic infection that causes secretion and suberification of the plant, which slowly dies. Against this pathology, there is usually little or nothing to do, except try to deal with specific systemic fungicides (based on the above-mentioned Tebuconazole, for example). Of fundamental importance is to move the affected plant away from the others and, in case it is too late to save it, throw away plant, soil and pot (unless you want to disinfect it with bleach).

 Root and collar rots  – They are caused by fungi in persistent hot/damp conditions and by water stagnations in the soil. They affect the roots of the plants and extend to the collar causing their rot and, consequently, the death of the plant. If taken in time, for example after having noticed a slowing in the growth of the plant and its deterioration, you can intervene by flaking the specimen, removing all the old soil and cutting off all the rotten roots and then let the plant dry for at least a couple of weeks in the air but not in the sun. If the rot has hit the collar, you can try a rescue by cutting the plant to the healthy part (i.e. until the pulp is white and has no dots or brown areas). It is essential to use a sharp cutter by disinfecting the blade with alcohol before each cut, to avoid infecting the healthy part. Also in this case, after this operation, you will have to leave the plant in a shaded but very ventilated place for some weeks, until the cut part is completely dry and scarred. At that point, you can place the plant on pumice to try to promote the rooting of the cutting.

 Pythium  – It is a fungus that attacks the seedlings bringing the roots and the collar to rot. If it is not too late to intervene, the plants should be flared, the old soil removed and the seedlings left to dry. Afterwards, it is possible to use a fungicide based on Previcur, both for preventive and curative purposes.

 Powdery mildew  – This is another pathology caused by fungi, commonly called powdery mildew. It develops in conditions of low humidity and temperatures above 20 degrees and spreads through the spores carried by the wind. It reveals with white/greyish pulverulent spots, which lead to the decay of the plant. Against powdery mildew can be useful nebulizations with water mixed with sulfur.

 Sooty Mould  – Also the sooty mould is caused by fungi, a pathology that leads to the production of a dark-coloured crust or to the formation of black powder, often on cacti areoles, at the base of thorns. Are affected by it some cacti, like Ferocactus, which produce honeydew, nectar secreted by the areoles. In case of smoke, it is possible to intervene with copper sulfur, either by spraying or manually, by cleaning the affected areas with a toothbrush or a cotton bud soaked in a solution based on water, sulphur and copper.

 Rust  – This name indicates a pathology, septoria, caused by a fungus called septoria. The symptoms are yellowish spots on the stem, more or less extended depending on the severity of the attack. They are created in conditions of poor ventilation and stagnant humidity. The rust seems to particularly affect Ferocactus latispinus during the winter. It can be controlled by providing the plants with maximum ventilation and low humidity. In case of attack it is good to move the affected plants, give them more air and intervene with copper-based products.

 Botrytis  – Botrytis cinerea, also known as “grey mould”, is caused by a fungus in conditions of persistent humidity and poor aeration. It creates spots initially dark green with yellowish edges. Then the spots are darker until they become brown or black and are covered with grey mould. The best prevention is a good recirculation of air and space between one plant and another. In case of an attack by botrytis, it can intervene with systemic fungicides in association with copper oxychloride. Isolate the affected plant immediately to prevent the spores from passing on to other specimens.

Animal parasites

Even against animal parasites, the best weapon remains prevention, understood as proper cultivation aimed at obtaining robust and healthy specimens. However, some bad encounters between our plants and some parasites (or lice, as they are commonly called) can always happen.

 Cochineal  – These insects are among the main enemies of succulent. They attack plants like the Opuntia, but they do not disdain the other Cactaceae. They can be of three types: waxy cochineal, mealybugs and shield. They usually strike the apex of the plants, but they can nest, also between the roots when the soil remains dry for long periods. In the latter case, the attack is more dangerous, because we only notice it when we repot or if we are very careful if we see that the plant has blocked the growth and is declining without any other apparent causes. The mealybugs suck the sap from the succulents, weakening them, and compromising their growth. The waxy cochineal nestles between the coasts of the Cactaceae or around the areoles, is a couple of millimetres long and secretes a layer of wax. The cotton cochineal, as its name says, produces small white woolly balls. It threatens the apex of the cacti or between the leaves of the succulents and sucks the sap. If the infestation is limited, you can manually remove the mealybugs or crush them with a toothpick. In the case of root cochineal, it is necessary to remove the soil, clean the roots thoroughly, shorten them and, immerse the root system or the whole plant for a few minutes in a contact insecticide and then let to dry for a few days before repotting in the new soil. The cochineal shield is more difficult to remove manually, which also reproduces quickly and, if left to do, can literally cover the plant seriously compromising its growth until it decays. It clings tenaciously to the trunk of the cacti, is white/greyish and has the typical shield shape. They can be removed with a toothbrush, or removed with a nail, but it is not always an easy action. Specific systemic insecticides, or summer mineral oil, can be used against mealybugs. It is also useful alcohol (diluted in water and nebulized), which dissolves the waxy protection produced by these insects and makes them more vulnerable to a subsequent treatment based on specific products. In case of radical cochineal, it is good to immerse the roots (or the entire plant) for a few minutes in a solution based on water and specific anti-cochineal products. When crushed, the cotton cochineals produce a red substance that was used as a textiles dye by Mexican populations.

 Red spider  – This is a small phytophagous mite (Tetranychus urticae), not visible to the naked eye. It proliferates in dry, warm conditions, so it can develop in the hot season if the waterings are very spaced, and the climate is particularly dry. It strikes the apex of the cacti, where the tissues are more tender, and causes secretion on the epidermis which assumes a grey/reddish colour. Growing up, the stem is chapped and aesthetically compromised. At the same time, a massive attack by the red spider can slow the growth of the plant and compromise its proper development. Good prevention against these mites consists in the cultivation of cacti in full sun so that the epidermis hardens and is less subject to the attack of the red spider. At the same time, outdoor cultivation encourages the presence of insects competitors able to contain the development of this mite. A red spider infestation can be countered by systemic and acaricide insecticides such as kelthane, dicofol and sulfur products. It is important not to use the same active ingredient often because the red spider quickly develops acaricide-resistant strains.

 Nematodes  – They look like little worms. They develop in fresh and humid soils and can penetrate inside the roots of the plants blocking the lymphatic flow and leading the plant to growth block, decay and death. They can be easily noticed only in case of repotting: the roots have swellings, nodules a few millimetres in size. As a preventive measure, it is advisable to take a good look at the roots of freshly purchased plants or during each repotting. In the presence of nematodes it is necessary to cut the roots as much as possible and throw the pot and all the old potting soil. Some growers recommend soaking the roots for about twenty minutes in water at 50°. When you notice the presence of these nematodes, often it is too late because they move from one root to another and eradicating them is quite difficult. It is not by chance that several experts advise throwing away the plant in case of an attack by nematodes.

 Aphids  – Fortunately, they do not frequently attack succulents. These are green or black insects that can weaken the affected plants by opening the door to viruses. Specific products (such as Movento) are easily found against aphids, although they can be removed with soapy water (for example, using a Marseille soap diluted in water).

 Metcalfa  – They are small white or pale green insects and appear from the middle of May. They suck the sap of the plants and can facilitate the onset of honeydew and soot. They can be counteracted with specific insecticides, such as those used against cochineal.

 Thrips  – They are very small so that it is almost impossible to see them with the naked eye. They usually attack the flowers, attracted by the pollen, causing dryness, malformation to the petals and favouring the attack by viruses. Against these insects, you can use blue chromotropic traps, or Marseille soap and water or specific insecticides (dimethoate).

 Swarming Fly  – The larvae of these Dipterans are dangerous for seedlings. In fact, they nest in the soil and attack the collar and the roots of the young plants, causing their decay and subsequently their death. The swarming fly is attracted by humid soils rich of organic substance (e.g. peat); for this reason, it can easily attack the seeds, which for the first months must have the soil always humid. The larvae of swarming fly are fought with specific insecticides to be administered together with the waterings.

 Snails and ants  – Among the potential enemies of cacti and succulents there are also snails and ants. Snails can cause considerable damage because they eat the fleshy leaves of succulents and can attack the apical part of cacti, which is more tender. When they are found, they must be immediately removed from the plants, whilst to keep them away, we can resort to the old system of the saucer with some beer, which attracts them and the stuns. There are also specific products in granules to be spread on the surface of the substrate: for snails, they are toxic and eliminate the problem before the molluscs attack the plants.
Ants are not dangerous, but they steal the seeds of succulents and are attracted to the nectar that the glands of some cacti produce (e.g., Ferocactus). They can also carry insect eggs that are harmful to plants. They contrast with specific insecticides, often powdered, to be spread around pots to keep them away.

Wondering what is the right soil for cacti and succulent plants? You can read here…

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L'articolo Diseases and pests of cactus and succulents: how to recognize them and how to prevent their attacks proviene da Il fiore tra le spine.