The spider mite is a predominantly phytophagous arachnid, which attacks various plants, both fruit and ornamental. It belongs to two different species, the first is called Panonychus Ulmi and the second, Tetranychus Urticae. The spider mite is considered a very dangerous pest for plants and with a high potential for infestation as it is able to reproduce very quickly and within a few days.
The two species of red spider Panonychus and Tetranychus attack herbaceous plants, shrubs and vegetables. Specifically, the red spider of the genus Panonychus attacks fruit trees and vines, while that of the genus Tetranychus affects tomatoes, beans, other legumes and soy.
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The spider mite is a mite or arachnid characterized by very small dimensions, ranging from 0.5 millimeters for females and even less for males. The body of this parasite is colored red in the adult stage, while in the juvenile stage, yellow or orange. On the sides of the back there are white bristles called tubercles, not present in the Tetranychus species. The red spider reproduces in oviparous mode by depositing about one hundred eggs per year. The eggs are fertilized in winter, and then overwinter in spring or summer. The larval stage of the spider mite is in the form of a neanide. Adult specimens and larvae feed on the upper and lower edges of the leaves and shoots of the affected plant. Their mouthparts are pointed and allow you to prick the infested plant parts to suck out the plant's nutrients.
Symptoms of the plant
Red spider mite infection occurs mainly on the leaves, which suddenly discolour on the upper edge, taking on a color similar to that of bronze. This stage leads to their drying and the consequent early fall. On the lower edge you can see the necrosis of the plant tissue or the appearance of whitish powdery spots due to the residues and excrements of the larvae, a sign of the successful colonization by the mite. On some plants, the infestation is concentrated at the edges of the leaf margin, which appears as if it were burned. In the tomato, for example, the burning of the leaves by the red spider causes the burning of the berries, as the sun's rays, without the foliar protection, penetrate more easily into the fruit.
Red spider mite infestation is favored by precise climatic conditions. The climates that stimulate the development and spread of this arachnid are hot and dry, characterized by absent humidity and rather scarce rains. It is precisely in arid climates that the spider mite is most widespread, representing a real calamity for horticultural crops.
Prevention to avoid spider mite infections is mainly linked to the issue of humidity: the more it will be present on the plants, the more likely it is that the spider will not spread. It is therefore advisable to increase irrigation during days that are too hot and dry and frequently wet the leaves and shoots.
The fight against the spider mite can be fought both in a natural way, using the so-called biological remedies, and in a chemical way.
There natural struggle uses mite predatory insects, such as other mites or ladybirds, while the chemical one uses chemical herbicides with a specific action. Among the natural methods of struggle we also mention already splashing water on the infested parts. The spider mite does not like water and if the colonization is not too extensive, you can intervene by spraying water on the parts of the plant attacked by the parasite or washing it entirely. The method of washing with water is effective in ornamental plants, but serves to eliminate the adult specimens and not the eggs, which normally hatch in the hot season. In crops and if the infection is rampant, it is necessary to proceed exclusively with the chemical fight.
On the market there are acaricidal products and insecticides that are also effective for arachnids. Often, systemic insecticides are used to eliminate the spider mite which, in addition to damaging the plant and the surrounding environment, also kill the potential predators of the mite, while the latter does not seem to suffer any damage. To be sure you are not mistaken, it is better to choose an acaridic because insecticides could prove ineffective as they are created to fight insects and not mites.
Among the acaricides against the spider mite are mentioned fenazaquin, etoxazole, abamectin and spirodiclofen. The first of two, from experiments carried out, act faster but also eliminate the antagonists of the mite. The other two act more slowly, but only on red spider mite species. To fight i red spider mites that infest ornamental flowering and potted plants, you can also use a product called Floramite, based on Bifenazate, a biodegradable substance. The suspension must be diluted in water and sprayed all over the plant. The frequency is two applications one week apart.
Red spider: Red spider of travertine
An insect that looks a lot like the red spider of plants but which unlike the latter is completely harmless is the red spider of travertine. This spider, so called in common jargon due to the fact that it is almost always found in low walls and stony ground, can be confused with the normal red spider but does not create any kind of problem either to plants or to humans.
You just have to pay attention to the fact that it stains when crushed and creates persistent stains that can permanently mark even the stones.
The red spider of the travertine is also a natural enemy of some dipterans (insects) that are eaten by the spider both in the larval phase and in the adult phase.