Mites are tiny spiders less than 1mm long. There are several types. Eriophyes (sap-sucking mites), with the help of a chemical, cause the tissues to clump together around their location on the plant. Tarsonemes deform the stems by attacking the tips and flower buds. Mites belonging to the tarsonemid family (Tarsonemidae) show a greater diversity of feeding habits than any other family of mites. Some species feed on fungi, algae, plants, as well as insects and mites. Those that live on plants can cause serious damage!
Red spider mites, Tetranychus urticae, are formidable little pests that can parasitize your indoor plants. They are not insects: spider mites belong to the Arachnida family, and more precisely to the order Acariens. Spider mites cause fine, light mottling of foliage. They weave a fine web around the plant and feed on the tissues of the plant and especially its sap. Spider mites feed on leaf cells, which particularly damages chlorophyll and reduces the photosynthetic capacity of plants, which is essential for their survival. The leaves thus injured appear pecked with tiny pale spots giving the foliage a dull appearance. Anyone with a sharp eye will see the beginnings of infestation by these discolorations of the foliage.
During heavy infestations, the leaves often covered with "spider mite webs" can lead to the death of the plant in the more or less long term. These parasites are hardly visible to the naked eye, because adult individuals are less than a millimeter in size! Their colors vary according to the plant from which they suck the sap: pale green or dark green, yellow, orange, red, dark brown.
The development cycle of tarsonemid mites includes egg, larva and adult stages. Larvae have three pairs of legs, adults have four pairs. The last pair of legs of males and females is different from the others and is not used for movement. The larvae remain in their larval cuticle for one to two days before emerging. This stage is often referred to as a fourth stage called a pupa, false pupa, or inactive nymph. The males use their four pairs of legs to transport the young female pharates (inactive nymphs) which are still in their larval cuticle. Mating takes place as soon as the adult female emerges from her larval cuticle. Tarsonemid mites have no eyes.
Female mites lay their eggs mainly on the underside of the leaf. The elongated oval-shaped eggs are firmly held on the surface and are rather large (about 0.07 mm) compared to the active stages. They are transparent and dotted with white dots. The mite larva resembles the adult insect, but is slightly smaller and has only three pairs of legs.
Upon hatching, the adult mite is about 0.2 mm long. It is large and oval and pale yellow or yellow-green depending on the type and amount of food eaten. Female mites have a white stripe on their backs.
Life cycle: In order to properly detect the spider mite and act quickly to control populations, it is important to know its life cycle. This pest can grow very quickly; it varies with temperature, humidity and host plant. For example, it takes 36 days at 15°C, 10 days at
25°C or 6 days at 35°C to complete a full egg-to-egg cycle. At 25°C, a female can lay up to 170 eggs, which gives a good idea of how quickly irreversible damage can occur. From August, the fertilized females, red-orange in color, hide and go into diapause to survive the winter. Both eggs and adults then go into overwintering mode.
* Diapause: Diapause is a genetically determined phase in the development of an organism during which it decreases the intensity of its metabolic activities.
Prevention, chemical control, biological and mechanical
Prevention is based on a simple principle: moisten! Spray the foliage of your plants, mites hate humidity! You will notice an increase in their presence, especially in winter, because winter heating dries out the ambient air in our homes. It is strongly recommended to increase the humidity in rooms where indoor plants are grown. The humidifier becomes our greatest ally in this cause! Another trick is growing above a humidifying tray. Or to have a lot of plants: as each plant releases humidity, the more plants you have, the more humid the air will be.
-Against the spider mite you can use another predatory mite called Phytoséiulus Persimilis. He is the most active of all and undoubtedly a true warrior! At a temperature of 15 to 25°C and fairly high humidity, this mite is as comfortable as a fish in water. Against this background, it can grow twice as fast as the spider mite.
* However, it is very specific and will quickly disappear in the absence of prey.
*Its lifespan with prey is about one month.
- Neem oil vaporization: Neem oil is biodegradable, does not create resistance in insects and is very economical. Neem, also called neem (Melia azadirachta or Azadirachta indica), is a very widespread tree in India. It is found in all hot climates. Its seeds are pressed to give a strong-smelling oil, the main active substance of which is Azadirachtin. Neem oil is also a natural insecticide to protect plants from pest insects. It can be used throughout the growing season. How does it work? Neem oil, and more specifically Azadirachtin, is effective on a large number of insects and mites, including caterpillars, some aphids, some thrips, mites including red spider mites, scale insects, and many Diptera and Hymenoptera.
It acts at several levels of the physiology of these insects:
• It paralyzes the digestive tract, and the insects can no longer digest what they have ingested: they stop feeding and die.
• It blocks molting in the larvae, which never reach the adult stage and die.
• It inhibits sexual reproduction, by blocking couplings.
The effects of Neem oil on the parasites are not immediate, you have to wait 2 or 3 days to see the death of the insects or their escape!
***You can make your own recipe by putting 5-10ml (1-2 tsp) of pure Neem oil in a spray bottle and topping up with warm water to about 100ml. Shake well before use to disperse the oil in water, then spray on plants.
Mites are not insects hence the ineffectiveness of insecticides. To overcome a violent attack, use the appropriate acaricides at weekly intervals for two or three treatments.
Visual and manual inspection is really important in our daily routine. It allows us to detect unwanted insects as well as any physical changes as soon as possible. We look at the top and bottom of the leaves, the stems and the soil. Particularly check new leaves, flower buds and new flowers which are most likely to be attacked by an undesirable insect. It is almost certain that an infestation starts with an insect or egg on a leaf! So, if during this inspection we eliminate this leaf with the insect that is there, there is no risk that the whole plant will be infested by the eggs or the young of the first insect!
Good luck with your fight plants lovers!