Pesticides: how to use them

In botany, the term pesticides refers to those products, chemical or of natural origin, used to protect plants from pests, diseases, insects of various kinds.
Most of these products are available on the market for amateur use, while some pesticides are used only in agriculture, or only by professionals.
We can distinguish three large families of pesticides: those useful for defense against insects and other animal pests, those to be used to combat the most common fungal diseases; and finally we consider the products used to disinfest the gardens from weeds.


Anyone who has a garden, or even a small balcony, on which he has cultivated few flowering plants, knows that unfortunately most of them can be periodically attacked by parasites of various types. The most widespread insects are undoubtedly the mites, which develop mainly in situations of hot and dry climate (which in reality are not insects, but arachnids, in fact they are also called red spiders); aphids, spread on flowering plants, vegetables, fruit plants, conifers; the cochineal, an insect well known by lovers of succulents: from the cochineal is extracted a very valuable dye, red, also used in the food industry; at one time the cochineal was “raised”, mainly on prickly pear plants, where it seems to develop in an excellent manner; caterpillars of various kinds, or other leaf miners, which often have a fairly rapid development, from the larval stage to the adult form; snails, especially those who grow a small vegetable garden, which can find young plants recently planted completely devoured. Many others are the insects widespread in the garden, even if their incidence is smaller than the previous ones; we remember the ants, even if in fact they do not damage the plants, these little workers can enter the house, and take advantage of bread crumbs or other remains they find on the floor; on plants the ants can be harmful because they live in symbiosis with the aphids, from which they suck the residual honeydew: to increase the honeydew produced by the aphids the ants also come to "raise" these insects, transporting them from one plant to another, and then widening the infestation.
Even the leafhoppers and the metcalfa cause damage on the plants, as well as the ostiorrinco, a small dark insect that lays the eggs in the ground: as well as other larvae (for example those of the beetle) those of otiorrinco feed on the roots of the plants; the adult form of the insect instead moves on the leaves, causing serious damage.

Fungal parasites

Also in this case there are many diffuse diseases, some of which seem to have a particular predilection for some types of plants: for example, powdery mildew spreads particularly on roses, especially in the case where water frequently remains on the leaf page during night hours; the bubble manifests very often on the peach tree, mainly in spring, in case of heavy rains and significant temperature changes.
Other widespread diseases are botrytis, various root rots, rust, grapevine blight, as well as various virosis and bacteriosis, which fortunately often save most of the plants cultivated by enthusiasts.
Some deficiencies that can be mistaken for diseases are nutritional deficiencies: the most famous is chlorosis, which occurs with particular frequency on acidophilic plants, when they are not able to absorb the right amount of iron from the soil.

Let's defend ourselves naturally

First of all we want to remember that the main useful remedy against insects and fungal diseases, is to cultivate the plants in the best possible way: let us plant them in the most suitable soil and in the place indicated for their health; remember to keep a good space between the plants, suitable to guarantee sufficient space for the plants to develop without intertwining, in addition to a good recycling of the air; in summer we try to water the plants during the first hours of the morning, avoiding to excessively wet the foliage; for specimens grown in pots remember to change the container, at least every two years, replacing all the soil with fresh and good quality substrate. We supply the right fertilizers, using a specific fertilizer for each essence cultivated by us, in the ways, times and doses indicated on the packaging of the fertilizer itself. We also avoid excessive care: too much water, too much fertilizer, too frequent repotting, risky pruning or plant transfers during the vegetative period.
Every time we buy a new plant we try to inform ourselves about the cultivation needs of this essence, and about the parasites that hit it most often: sometimes it is sufficient to vaporize with demineralized water a plant subject to the attack of mites, to prevent the presence of such insects .

Choice and use of insecticides

The range of products available for plant lovers is very wide; there are fungicides and aids that penetrate inside the tissues of plants, which therefore have a very long duration, up to a few months; while the most widespread insecticidal products act by contact with insects, and their action takes place for a few hours or for a few days.
Whether it is a chemical product, a "grandmother's remedy" or a product to be used in organic farming, in general it is advisable to use insecticides only in case of real necessity, or only if you have seen numerous insects on plants, and only if these have suffered significant damage. It is advisable to avoid the use of insecticides as a prevention, especially if it is an insecticide that performs their action by contact with the insect: by distributing them on the plants we do nothing but disperse into the environment substances that can have a harmful effect on the ecosystem.
When we notice an insect on our plants, a yellowing of the leaves or spots, we take a sample, insert it in a transparent bag, and close it tightly; so let us go to a garden center or a well-stocked nursery, and ask an expert for advice, to be certain of the type of parasite that lurks on our plant: it is advisable to avoid broad-spectrum insecticides, which are often harmful even for the our small animals and for the useful insects that live in our garden.
Therefore we use specific remedies, only on manifest infestations; It is also a good idea to avoid spreading any insecticide or fungicide product in the garden during flowering: in this way we will avoid chasing away or killing pollinating insects, such as bees.
For potted plants we can make use of systemic products, which enter the plant's tissues, to be mixed with the water used for watering; these products are generally used at the end of winter, and generally only one intervention is sufficient for the duration of the vegetative season.

Selection and use of fungicides

Also in this case we can make use of fungicides that simply cover the leaf blade, protecting it from infestations, and other products that instead penetrate inside the leaf blade, guaranteeing a more prolonged defense over time.
We always use only the fungicide necessary to eradicate the disease that has manifested itself on the plant, avoiding as far as possible there are broad spectrum products.

In the case of fungicides, however, it is possible to intervene with products that act as prevention against fungal diseases, given that some spores of very widespread diseases remain on the ground around the plants, nestle among the fallen leaves in winter, and then spread very quickly with the arrival of the warm season.
Also in agriculture we tend to use wettable powders of copper and / or sulfur, with which to vaporize the foliage of plants subject to powdery mildew, rust, downy or bubble, and also the surrounding soil; this type of intervention is practiced in autumn, after the fall of the leaves, or at the end of winter, before the buds become enlarged. This type of preventive fungicide treatment, based on sulfur or copper, is also practiced during the vegetative season, away from the blooms, whenever there are obvious changes in temperature, or long periods of intense rainfall.
As for other types of fungicides, the interventions are carried out only when the disease has manifested, and in this case also avoiding the flowering periods.

Pesticides: How to intervene

Once we have discovered the type of parasite that lurks on our plants, and the product that is most suitable to defeat it, we prepare the solution to be sprayed on the plants. As said before the applications of pesticides are practiced far from the flowering periods; during the hottest months of the year the applications of products for vaporization on the foliage of the vegetation, are practiced during the first hours of the morning, when the air is still fresh. We avoid too hot and sunny days, and we also avoid vaporizing the plants before the rain, which would nullify our intervention.
When preparing the pesticide solution, we strictly adhere to the illustrative leaflet of the product we have chosen: many researches are carried out before marketing a product to be used on the plants, these researches are aimed at finding the best possible dose to use; it is not said that doubling the dose of the product we will also double the effect: many pesticides, if used in inadequate doses, can be harmful for useful insects, and also for the same plants on which we are using them. So we lose a little of our time to inform ourselves about the most suitable doses and the interval between two product applications, should they be necessary.
We also remember that if we use any product against insects or fungal diseases, on plants that we will then use in the kitchen, whether it is vegetables, fruit plants or simple aromatic herbs, we will have to wait a few days before being able to use any part of the plant itself for feeding: this interval is indicated on the label as a "waiting period", after which we can start to taste the tomatoes from our garden without any problems for our health.