Taxonomic placing: Acari, Prostigmata, Tetranychoidea.
Common name: Spider mites.
Geographical distribution: Cosmopolitan, with about 1200 described species.
Morphology: Spider mites are about 0.4-0.6 mm in length and vary in color, being usually green or red.
Life history: Spider mites are so-named because of the silk webbing produced by some species in the subfamily Tetranychinae. The webbing protects individuals or colonies and is used for dispersal, enabling long distance migrations. The populations of the more common species are characterized by cycles of colonization by mated females, followed by rapid population growth, localized over-exploitation of the host, and subsequent dispersal. Total developement of the different the species may require from 2-3 weeks to several months (including diapause); reproduction is by arrhenothoky.Females of various species lay from a dozen to over 100 eggs each.
Economic importance: The spider mites include major plant pests, infesting and damaging fruit trees, vegetables and ornamentals. Their damage is due to puncturing plants and sucking out the cell components, causing chlorophyll depletion. Typical symptoms include stippling and/or speckling of leaves, along (in some cases) with the accompanying webbing. In consequence growth is retarded, flowers wilt, and the quality and quantity and quality of the crop are affected. Even small necrotic spots that consist of aesthetic injury, reduce the value of ornamentals. One species, Tetranychus linterius Dufour, is beneficial, having been used as a biological control agent against gorse (Ulex europaeus L.) in New Zealand.
Chemical control: Injurious spider mites may develop rapid and extensive resistance to pesticides, but botanical compounds and insecticidal soaps may still control them.
Biological control: Injurious spider mites are attacked and sometimes controlled by many natural enemies. These include mites, like Phytoseiidae and Stigmaeidae, and predatory Coccinellidae, Thysanoptera and Cecidomyiidae. Spider mites are sometimes infected by entomopathogenic fungi and in rare cases by viral diseases.
Tetranychidae included in this compendium
Ben-David, z., Ueckermann, E.A. and Gerson, U. 2013. An annotated list of the spider mites (Acari: Prostigmata: Tetranychoidea) of Israel. Israel Journal of Entomology 43: 125-148.
Bolland, H.R., Gutierrez, J. and Flechtmann, C.H.W. 1998. World Catalogue of the Spider Mite Family (Acari: Tetranychidae). Koninklijke Brill NV, Leiden, the Netherlands, 392p.
Leeuwen, T.v., Vontas, J., Tsagkarakou, A., Dermauw, W. and Tirry. L. 2010. Acaricide resistance mechanisms in the two-spotted Tetranychus urticae and other important mites: A review. Insect Biochemistry and Molecular Biology 40: 563-572.
Migeon, A. and Dorkfeld, F. 2006-2015. Spider Mites Web: a comprehensive database for the Tetranychidae. http://www.montpellier.inra.fr/CBGP/spmweb
Zaher M.A., Gomaa E. A. and El-Enany M. A. 1982. Spider mites of Egypt (Acari: Tetranychidae). International Journal of Acarology 8: 91-114.