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Plant diseases: when the cause is not the parasite


The plant diseases they can depend on problems of temperature, lack or excess of water (which is very frequent), lack or excess of light. Or even from nutritional aspects, from poorly used pesticides or from toxic substances present in the air or water. In short, it is not always the fault of the parasites: sometimes the causes of plant diseases they are typically environmental and it is not infrequently the 'gardener' who puts his own.

So let's see one by one the possible non-parasitic causes of plant diseases, to learn to recognize them and to remedy them.

Plant diseases: too little or too much water

Let's start with this which is the most frequent cause of diseases of indoor plants. Sometimes we overdo our water care and literally drown our plants. Other times it is too low humidity in the air, a typical situation in apartments, that causes damage.

Prolonged stagnation of water in the ground (the saucer is not a mosquito pool!) Causes asphyxiation of the root system, recognizable by the deterioration and discoloration of the leaves and shoots. Furthermore, too much water favors the development of many fungal diseases which we will then have to fight with fungicides.

The opposite situation, ie the lack of water in the soil, causes the plants to wither with a reduction in resistance to parasitic attacks. The advanced symptom of this withering is the appearance of necrosis on the leaf blades starting from the edges and tips.

The thing to know is that plants don't all have the same water needs. Some like water, others less so. Some like a soil that is always moist, others to be wet a lot but rarely and then dry. Consequently, the waterings must be personalized and a good advice, to save time and facilitate things, is to keep species that have the same needs close together. Then pay attention to the quality of the water, which if it is that of the tap is more often than not too calcareous. This is especially a problem for acidophilic plants (gardenias and azaleas for example) which cannot withstand 'hard' water.

Plant diseases: too hot and too cold

If the temperature is too high, the plants stop growing, the more delicate parts become necrosis and the leaves, flowers and fruits fall off. On the other hand, when it is too cold (compared to the values ‚Äč‚Äčindicated for each individual species) the leaves tend to turn yellow and curl up, the shoots struggle to open and tend to necrosis.

It is necessary to re-establish the correct conditions (which varies from species to species) but without sudden changes in temperature (do not constantly move the plants from one side to the other). These are equally deleterious and can cause splitting of branches and trunks even in large plants and trees.

Plant diseases: too little light or too much light

Plants in lack of light tend to stretch excessively and abnormally, the shoots are weak and stunted. Flowering and fruiting are also limited. On the other hand, excess light can be a serious problem for undergrowth plants that normally live in shady areas. Symptoms of exposure to too bright light are burns, even extensive burns, discoloration and hardening and of the leaves, which tend to remain small. Be careful not to confuse light with the sun: many plants (typically those for apartments) need a lot of light but cannot be exposed to direct sunlight.

Plant diseases: too much fertilizer or too little fertilizer

Together with errors in irrigation, excess or lack of fertilizer are a classic problem of plants in the house. Typical is the case of too much nourishment due to an excess of concern, like the grandmother who stuffs her grandchild with sweets to make him happy. The result is 'obese' plants which, unable to gain weight, develop in an unbalanced manner, leading to necrosis of leaves, buds and flowers.

Conversely, a lack of nutrients leads to a slowdown in growth and a change in the color of the leaves. However, it depends on the type of deficiency, which must be identified in order to intervene with a targeted fertilization that restores the balance of the missing element without exceeding with the others.

Starting with the macroelements, nitrogen, phosphorus and potassium, the situation is roughly this: if there is no nitrogen, the plant slows down its growth and the leaves tend to turn yellow. A bluish color of the leaves, with shades tending to purple, is instead the symptom of a lack of phosphorus. The lack of potassium is manifested by slowing growth, the curling of the leaf margins and a stunted coloring of the flowers and fruits.

Even the lack of microelements, iron and magnesium in particular, manifests itself with yellow leaves; especially in the spaces between the ribs, which tend to stay green longer. To understand: if the youngest leaves turn yellow first, it is because there is no iron; if, on the other hand, the discoloration begins from the oldest and basal leaves, magnesium is missing.

By correcting the iron deficiency with fertilizer, which is called chlorosis and is typical of calcareous soils, the young leaves will turn green again. Not so for magnesium: adding a targeted fertilizer will restore balance and health to the plant, but the yellowed leaves will never turn green again.

Feeding regularly and in the right doses of a balanced fertilizer helps keep the plant healthy and prevents most problems. For a preventive action it is certainly preferable to fertilize the soil, possibly leaving the timely and timely correction of possible deficiencies to foliar fertilization. Below you will find a good organic product that can be purchased online.

BioBizz Bio-Grow complete liquid fertilizer

Plant diseases: damage from pesticides

They deserve a separate chapter plant diseases caused by an excess of pesticides or medicines that we have used to intervene on other problems, typically fungal or parasitic infestations. The symptoms are leaf necrosis, discolorations or particular colors depending on the substances used.

The rule is to adhere to the doses and indications given on the pesticide packaging (better less than more) and never administer the substances under the sun and in the hottest hours of the day. Even an excess of 'natural remedies' such as macerates, infusions and decoctions etc ... can cause problems for the plants and even if they are less aggressive preparations, we must not overdo it.


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