Spider Mites aren't insects. They're actually more closely related to spiders, both of them belonging to a class called Arachnida. Spider Mites in the family Tetranychidae feed solely on plants. Many groups in the family are pests in agriculture and horticulture. Spider Mites get their names after their ability to produce layers of silk webbing. The web protects colonies and is also the primary method of dispersal between plants. In most cases, Spider Mites are tiny, and species can be challenging to tell apart by a glance. Many, however, will specialise on one or two species of plants. The Glasshouse Spider Mite is by far the most common species. It's well known for its broad-host-range and is especially common on plants kept indoors or under glass. A mated female Spider Mite will colonise a plant, before laying eggs. Dependent on species, female mites are capable of laying 12 to 100 eggs. From here follows rapid population growth and exploitation of the plant.
Adults: Small, spider-like mites that can be red, green or yellow, often accompanied by sheets of fine webbing.
Yellow/ brown stippling-speckling of leaves. Fine dusty webbing covering branches and leaves. It's sometimes possible to see small little arachnids in the webbing. Stunted or abnormal growth. Reduced quality of yields. Reduced flowering. Wilting.
On plants kept outdoors, Spider Mites are sometimes controlled by other insect predators. Attract these predators to your garden by incorporating a mixture of native plants (that can be hanging or climbing, too!), shrubs, trees and grasses. Homemade insecticides are easy to make, gentle, and an excellent first attempt for controlling infestations; particularly on indoor plants. They can be made by combining either of the following with 2 cups of water: garlic puree, chopped chilli and bio-washing up liquid. The more ingredients used, the stronger the pesticide. Rubbing alcohol, or isopropanol, can be useful when used against sap-sucking pests, such as Spider Mites. Neem or other horticultural oils can be effective at tackling spider mites.
In some cases, Spider Mites can quickly develop resistance when pesticides are used due to their quick rate of reproduction. If you have a Spider Mite infestation, it's recommended to attempt an insecticidal soap and organic pesticides first off. Organic pesticides contain botanical compounds called pyrethrums, they tend to be more gentle and usually require reapplication. Make sure to always read the bottle instructions carefully. If you intend to eat your crop, make sure it's listed on the label. Plants in flower shouldn't be sprayed, as there is a risk compounds can harm beneficial insects.