Plant diseases


Plants and living organisms

Plants are extraordinary living beings that do for us much more than what we do for them, after all, there is to be honest: man never does anything for other species, at most he supports and studies them but only to see if he can gain anything in terms of food, nutrients, or whatever. However, leaving out this discussion that does not touch us here, let’s go back to talking about what plants do for us: they are a source for us of food, nutrients and also other substances beneficial for our health, they delight us with perfume. flowers and their colors, but above all they provide us with an incredibly high quantity of oxygen every day, without which we humans could not survive more than a minute. This happens through that amazing mechanism that goes by the name of chlorophyll photosynthesis: thanks to the substances they absorb from the soil and the lymph they produce, the plants exploit the light absorbed by the sun to initiate a series of chemical reactions that lead to the absorption of anhydride. carbon dioxide and its transformation into oxygen. From our point of view it is a godsend, as we use oxygen even only when we breathe and if there were no plants to regenerate it it would be a big problem.

Having established that plants perform several extraordinary works for us, let’s move on to see what are the enemies of these extraordinary living beings; in reality there are many these enemies, and they have very disparate forms, both as a structure and as an attack on the plant, but both nature and we humans have learned to defend ourselves well. The enemies of plants could be divided into four categories: animals, insects, fungi, viruses. As far as animals are concerned, it is usually small species, which attack the plant by eating it voraciously (and therefore destroying it) or for example by digging tunnels between the roots which limit its absorption. Insects attack plants almost always through their larvae, voracious eaters of leaves and fruits. Fungi can both attack the plant and parasitize it by absorbing all the nutrients and use it as a support to grow without parasitizing it. Viruses, on the other hand, are real carriers of diseases, and as happens for humans, if they manage to penetrate the plant then they infest it and are real pains because they are often dangerous diseases also due to the lack of developed solutions.


The smokinessis a classic infestation of several plants, whose name is the result of a popular tradition and for this reason corresponds in a certain way to a description of the disease: it appears as a dark gray / blackish layer on the outside of various areas of the plant, just like the browning due to the accumulation of smoke and ash (popular culture often opts for these denominations, such as the wording “bad white” for powdery mildew, to see the card on our website). In reality, this brownish layer is nothing more than the mycelium (i.e. the outer part) of a fungus, or rather of a fungus of the saprophytic genus, that is, which does not parasite the plant but uses it only as a support to grow. Let’s say immediately that the fumaggine does not cause direct damage to the plant, in fact eliminating it mechanically with elbow grease and specific detergents you can see the healthy leaf below; however, there are two indirect damages: the first is that since the mycelium often covers the leaves, it prevents light from reaching the surface and therefore effectively prevents the plant from carrying out chlorophyll photosynthesis, thus preventing it from continuing to grow at its natural rate ( and this also affects the production of flowers and fruits).

More information and solution

The second indirect damage of the smoke is actually its … cause: in fact the fungus attacks areas of the plant covered by a viscous and glucose layer, called “molasses” and caused by the attack of various types of mites and other insects. So when the plant is affected by smoke, it means that it has already been infested previously by these annoying and parasitic insects, whose damage is instead direct because they destroy the plant from the inside with their larvae that “steal” many nutrients. The solution against smokiness is specifically a generic antifungal product commonly sold, but the real solution is to eliminate the underlying mite and aphid infestation, both because it is more harmful to the plant and because if the insects remain with their molasses, the fungus may recur. In this regard, copper treatments are indicated. The damage of smokiness is relatively limited to aesthetics, but often the consumer is (rightly) pushed to refuse a fruit, for example a lemon that has a sticky black layer on the surface, even if the inside is perfect. A condition to avoid for general development is excessive humidity without air exchange, so care must be taken with pruning.

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