Parasites and Diseases

Parasites and Diseases

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Plants can be affected by various adversities: both climatic and parasitic. Despite all the care and attention we reserve, plants, trees, bushes and flower beds can show strange symptoms ranging from leaf yellowing, to premature drying up of the trunk or failure to flower. Sometimes the adverse weather conditions interact with parasites, which proliferate in particular climatic conditions. Some insects, for example, such as aphids and scale insects, attack in arid or indoors environments. Scale insects, in particular, are widely used in greenhouses. The damage that pests cause to plants is immeasurable, both from an aesthetic and a productive point of view. Massive invasions of insects have often caused the loss of tons, or worse, of tons of crops. Methods to combat i plant pests they must therefore envisage strategies aimed at preventing or eradicating them from their first appearance. Our preventive strategy instead, as a magazine dedicated to gardening, is to dedicate a wide and in-depth section to the infamous plant parasites. Parasitic plant diseases can have many causes. These include unsuitable climate and terrain, excesses or lack of fertilizer or irrigation, crop errors in grafting or pruning, crop negligence and cultivation in poorly adapted environments. For the parasitic disease to manifest itself, it is therefore necessary for a negative condition to occur that can cause stress, weakening or suffering in the plant. It is true that, in some cases, parasitic pathologies can occur without any apparent cause. This is the case, for example, of the downy mildew of the vine, a fungal disease that massively affects the vines cultivated in Italy. Strangely, the American vine seems to resist the downy mildew, so much so that in the national cultivations it is more and more often used to use grafts of American vines. plant pests they are usually divided into larvae, insects, fungi, viruses and bacteria. The larvae are actually the offspring of adult insects. At the larval stage, some insects can indeed be particularly harmful to plants. Think, for example, of the larvae of the processionary moth, which lays eggs in the branches of the shrubs. After wintering, the larvae feed on the branches and leaves of the affected plant until they completely defoliate it. The disease is called "processionary" because, during the feeding activity, the larvae move all together and in a row in a sort of procession. Mushrooms are also among the most feared pests of plants. Grouped into thousands of species, the fungi tend to attack different plant species: almost no one is immune. Mushrooms often appear as a secondary insect infection. The latter can produce substances that stimulate the spread of the fungus throughout the plant. Mushroom diseases include powdery mildew, or mal-white, downy mildew, gray mold, rust, botrytis, fumaggina, scab and anthracnose. Fungal diseases are often difficult to eradicate, especially in the case of massive and overt infection. Crop damage from fungal diseases can be very high and this is why we generally tend to prevent the appearance of these diseases. In most cases, fungal diseases develop in conditions of excessive humidity and heat, other times they can be the consequence of cultural errors, such as excess water, or errors in pruning. Some fungi penetrate the plant tissue following cuts made with blades that are not very clean or not disinfected. Even pruning that is too aggressive or with imprecise cuts can weaken the plant, making it an easy prey for parasitic fungi. There are many insect pests that can affect plants. Among the most widespread it is worth mentioning aphids and scale insects. The first are also called "plant lice", due to their appearance made of small legs and an almost fluorescent back. There are several species of aphids, some have yellow backs, others green, others still black. These insects, like cochineals, which instead have an oval and hard back, feed on the sap of the plant, removing energy and leading to premature drying. Aphids and cochineals develop as a result of water shortages and dry and dry environments. Plants can also be attacked by some species of beetles, insects that are also commonly called "cockroaches". Beetles can also be winged. Some of them are known to be skilled devourers of branches and trunks. Viruses and bacteria can also be counted among plant pests. The former do not spread easily, but only due to cultivation errors. Virus diseases include virosis, or virosis. It is a group of diseases caused by various viruses. The latter can infect and hit plants in the same way as men. The causes of plant viruses are often linked to the use of contaminated tools. Viruses are often deadly to plants, given the impossibility of treating them with specific treatments. The treatment against plant diseases is therefore strictly preventive. Even bacteria can seriously damage our plants. Bacterial infections, as well as viral infections, can be caused by cultivation errors, but also by the action of insect pests. The latter, especially the species endowed with a sucking and biting mouthparts, can inoculate different types of bacteria in the plant. The plants most affected by bacteria are fruit plants, vegetables and ornamental plants. Bacterial plant infections are called "bacterial". Bacteria can deform the plant to the point of causing the appearance of galls and new growths that are real plant tumors. The symptoms caused by plant parasites change depending on the responsible agent and the affected plant. For some parasites, the symptoms may be similar. Aphids and scale insects, for example, during their attack produce a sugary substance that covers most of the plant. This substance, which also attracts ants, is called "honeydew". Other symptoms of plant diseases and pests can be the yellowing of the leaves or the spots on them. These spots, which may be more or less large, change in shape and color, based on the responsible infectious agent. The pink blight, for example, causes purple spots on the leaves. Fumaggine, on the other hand, causes the formation of a grayish or blackish smoke along the entire leaf surface. Hate or white mal is distinguished by causing, in the plant, the formation of starchy and whitish spots or spots. Furthermore, certain symptoms may be similar to those caused by other parasites. The whitish stains similar to flour and cotton, can also be formed due to the attack of the cottony cochineal, a parasitic insect composed precisely of a white and floury back. The symptoms of virosis are diverse and varied. In some plants, the infection manifests itself with yellowish spots on the leaves, in others, with reddish spots. The same variability of symptoms also for bacteriosis. Depending on the bacterium responsible, the symptoms can range from small dark spots to total browning of the leaves. Cancer is a disease characterized by an uncontrolled proliferation of cells. The disease, as well as in humans, can also occur in plants. In plant species, however, cancer is a secondary pathology caused by other infections and other parasites. They cause plant cancers, viruses, bacteria and fungi. The action of these infectious agents is able to radically modify the DNA of plant cells, causing an uncontrolled reproduction of plant tissues. Plant cancer, in addition to causing cultural damage, also causes aesthetic damage. Swellings and new growths in branches and shoots can also destroy the aesthetic appearance of the most beautiful and decorative plants. Within the section dedicated to plant pests we will talk more in detail about strategies to prevent attacks by infectious agents on plants. The most important prevention involves the setting of correct cultivation techniques. The plants must therefore be grafted and pruned with well cleaned and disinfected tools, both before and after use, and healing or quickly covering the wounds of the cuts. These wounds must not be too large and above all must be done without burrs. Other preventive strategies include the administration of the right dose of water and fertilizer and the cultivation of the plant in a suitable environment. If an acidophilous plant, for example, that loves acid soils, was cultivated on calcareous soils, it would soon develop excess limestone pathologies. Excess limestone causes ferric chlorosis, or lack of iron in the plant. Chlorosis is manifested by leaf yellowing. Preventive strategies against parasitic fungi also include treatments based on copper and sulfur, while those against insects even include the use of antagonist insects. They are antagonists of parasitic insects, some wasps and ladybirds. The fight against plant pests always depends on the responsible agent and the type of plant. At the initial stage, aphids and scale insects can be fought by spraying the leaves with water, washing them with a little soap or by manually removing the insects. Massive attacks require the use of specific insecticides. Some of these are based on pyrethrum, a natural substance extracted from daisies. Pyrethroid-based insecticides are also called "pyrethroids". Administered on plants, pyrethroids usually have a neurotoxic effect, ie they block the insect's nervous system and prevent it from even breathing. Other natural and chemical methods of fighting plant pests are contained in the individual articles of our section.
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  • Plant pests

    In this section we will talk about the main pests that attack plants causing them more or less serious damage. Spi
    visit: plant pests
  • Plant diseases

    Even the healthiest and most luxuriant plant can be a victim of diseases caused by animal or vegetable parasites: fungi,
    visit: plant diseases