Red spiders

Definition

Red spiders, also called spider mites, are not insects (insects have only 6 legs), but rather cousins of spiders. They belong to the class Arachnida.

More than 1200 species make up the family of red spiders. More than 100 are pests and 10 are major pests.

The best known of the pests is Tetranychus urticae (also known as two-spotted spider mite, weaver mite, red spider and yellow spider). Reproducing at a phenomenal rate, it can cause considerable damage very quickly.

Red spiders have a pointed mouthpiece that is used to suck sap. They feed by penetrating the plant tissue with their mouthpiece. Dense populations can cover the entire plant with their web. However, these webs also allow them to move.

Proliferation of red spiders

Spiders love indoor plants, even in closed boxes, their small size allows them to sneak through fans, extractors.

Red spiders (most of them) spin a silky web. When they infest plant foliage, they damage plant tissue by creating yellow, necrotic spots that coalesce until they infect the entire leaf. The leaf turns yellow, withers and eventually falls off.
Some other varieties of mites do not spin a web, but rather live in the apical buds of the plant. The damage they cause does not show up until it is too late.

Each female red spider has a life span of 4 weeks, laying 10 to 20 eggs per day (80 to 120 in total). Their eggs cling to the web. The six-legged larva hatches 3 to 15 days later. The newly hatched larvae are almost transparent and have bright red eyes. Over the next 4 to 5 days, they molt three times; from protonymph, to deutonymph and finally to adult. Adults and nymphs have 8 legs.

They suck the juice from the cells causing yellowing, necrosis and leaf drop. They have eight legs and tend to move very slowly.

Symptoms

The eggs of red spiders are about 1.4 mm in diameter and transparent. Later, they become dark opaque. When it is time for the larva to emerge from the egg, they turn a straw color.

The first way to detect a red spider attack is to spray water on the foliage with a fogger to reveal any webs. Red spider mites thrive best in dry, warm environments.

To confirm the presence of spider mites. Red spiders are so small that they can be very difficult to see. However, one method you can use to confirm their presence is to take a sheet of white paper and place it under the plant you suspect may be infested and gently shake the stem of one of the leaves.

A number of red spiders should fall onto the paper. It is easier to observe them with a magnifying glass.

They are usually not visible, so look under the leaves with great care. Use a microscope in case of doubt.

The first visible symptoms are the appearance of small yellowish or whitish spots, mainly around the midrib or wider veins on the leaf. As these spots grow and develop, the empty cells provide a transparent white or silvery tint on some parts of the leaf.

Red spiders (identifiable by the silky webs woven into the leaves) show a variety of colors, including red, green, yellow and brown. Be on the lookout for red spiders with spots on their backs - these are known as two-spotted spider mites and can be particularly difficult to get rid of.

Some spiders do not spin webs.

How to control red spiders?

Red spiders love everything that grows in greenhouses, indoors, potted plants near windows. Red spiders look for moisture in the leaves of the plant in dry weather.

It is important to control humidity (>60%) and coolness (<25°C) as red spiders love dry and dusty periods. In addition, natural predators of red spiders require high humidity. Also, keep the garden area clean and remove all plant debris and weeds from the growing area. Do not give red spiders new hiding places. In particular, remove all broadleaf weeds. Remove all debris remaining after cutting. This includes plant stumps, dead leaves and any other plant material.

Water stress can also be a cause of red spider mites.

When you suspect red spider mites, prune and discard infected leaves. Give the plant a good cleaning with a mixture of alcohol and soap. Or pure lukewarm water with washing up liquid. Repeat the treatment several times a week.

Wash and dry houseplants regularly. Since it's fairly easy to clean houseplants this way, this can be the most effective non-toxic method of ridding your plants of spider mites.

Use a water-soaked sponge to wipe down individual plant leaves or fill a spray bottle with water and spray the underside of the leaves.
Reapply the soap solution six days later if the invasion continues. You should be aware that some plant species are particularly sensitive to soap, so consider testing the soap solution on a small area of the plant before spraying it everywhere.

Getting rid of red spiders can be a challenge. Be persistent and try not to inadvertently create the conditions that red spiders prefer (heat, shelter, humidity for most red spiders, very dry for others).
Some plant viruses are transmitted by red spiders. This is another good reason to get rid of them.

Anti-insect treatments also exist.

Biological control

Red spiders have several natural predators that can help control populations. You can also use natural predators: predatory mites, bugs, ladybugs, and lacewings.