red spiders
Falsely named red spiders, probably because of their 8 legs, these undesirables are not insects, but mites of the weaver spider mite family. These spider mites include two species that are very similar both in terms of biology and in terms of damage: Tetranychus urticae which are yellow and Tetranychus cinnabarinus which are the brick red spiders we are talking about here.
On sunny days, these biting-sucking mites parasitize plants, trees and shrubs, but especially indoor plants or plants in greenhouses. They feed on the tissues and sap of plants. Hardly visible to the naked eye, adult individuals measure less than a millimeter. These red spiders can be red as their name suggests, but they can also be green, yellow, brown, etc. depending on the sap of the plant they feed on.
Development conditions
Spider mites appreciate a rather hot and dry atmosphere. This is the reason why they are often encountered in houses, especially in winter when the heating is on, but also in verandas. Outdoors, plants placed on the ground or on a sunny windowsill are more frequently victims of spider mites.
Under high temperature conditions, the development of these mites poses a major problem as heat tends to accelerate their proliferationsince the eggs laid, a dozen per mite, will then incubate in just a few days before hatching to give birth to new mites capable of laying eggs in turn, which can give rise to a massive infestation very quickly.
Since red spider mites are not very mobile, they move little from one plant to another, however, it is possible that an infested plant contaminates other plants nearby or you yourself may be responsible for their transfer. from one plant to another if you use the same cloth to dust them, for example.
Acknowledge their presence
At first, when you notice that one of your plants is starting to dry out for no apparent reason, you can start wondering about a possible spider mite attack. If this is the case and you do not act, your plant will eventually die, because these mites deprive it of its sap by sucking it up. But before this last stage, other signs can alert you and encourage you to take action:
- You may notice yellow or white dots on the leaves which correspond to the points where the mite has stung to suck the sap. Then the leaves turn completely yellow or take on a silver-gray tint, before withering and falling. Small holes may also appear.
- You may also notice fine cobwebs woven between the leaves of the plant. They are not very visible at first glance, but by misting the plant you can see them more distinctly, as they retain the water drops.
- Scrupulously scrutinize your plants and especially the back of the leaves, because this is where they are placed.
- It is possible to verify their presence by having a white cloth under the pot before shaking off the leaves of your plant. This will allow you to check whether any mites are falling out of it or not.
Prevention and treatment
Prevent
- We have seen it, spider mites hate humidity. It is therefore important to create an environment that they do not like. To do this, mist your indoor or greenhouse plants regularly. Similarly, for plants in your garden, water as soon as a dry spell sets in. If the infestation you’re dealing with is low, that may be enough to curb your problem. Do not hesitate to install your flower pots on a bed of gravel which will maintain a humid atmosphere near the plant.
- Avoid nitrogen fertilizers or potash which make the leaves more attractive to spider mites.
- You can also count on baking soda to repel these mites, but also other undesirables, such as aphids, among others. To do this, dilute 10-20 grams of baking soda in a liter of water, add 3 tablespoons of oil. Spray this repellent on your plants once a week.
- As a preventive measure, outdoors, you can regularly spray your plants with nettle manure.
Heal
- In biological control, it is possible to use a predator of the red spider which is Phytoseiulus persimilis. Generally, once it has destroyed the parasite population, it dies of starvation.
- You can dilute rosemary essential oil in waterthen spray this mixture on the whole plant.
- Similarly, you can treat the affected plant with black soap. It has the effect of clogging the respiratory pores of these spiders which end up asphyxiating. To do this, dilute 5 tablespoons of black soap in 1 liter of water, then spray on the plant.
- A garlic decoction will also be a good solution against red spider mites. To do this, macerate 30 g of garlic per liter of water, then spray the mixture on the plant after having diluted it to 30%. Repeat the treatment every 3 days for 15 days to destroy all specimens, as well as hatching eggs.
- Remove damaged leaves as you go by mites and burn them.
- In the case of a more advanced infestation, chemical treatments can be used. However, this type of treatment is not always effective because red spider mites have developed resistance to these types of treatment. In addition, their use is controversial for both environmental and health issues. These are specific acaricides based on dicofol or cyhexatin. There are also solutions obtained from wettable sulfur to be sprayed on the plant. These solutions are not recommended, either.