Spider mites are members of the Tetranychidae family, which includes about 1,200 species. They are part of the subclass

Acari Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear ...

(mites). Spider mites generally live on the undersides of leaves of

plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...

s, where they may spin protective silk webs, and they can cause damage by puncturing the plant cells to feed. Spider mites are known to feed on several hundred

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

of plants.

Description

Spider mites are less than in size and vary in color. They lay small, spherical, initially transparent eggs and many species spin silk webbing to help protect the

colony In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the ''metropole, metropolit ...

from predators; they get the "spider" part of their common name from this webbing.

Life cycle

Hot, dry conditions are often associated with population build-up of spider mites. Under optimal conditions (approximately 27 °C), the two-spotted spider mite can hatch in as little as 3 days, and become sexually mature in as little as 5 days. One female can lay up to 20 eggs per day and can live for 2 to 4 weeks, laying hundreds of eggs. This accelerated reproductive rate allows spider mite populations to adapt quickly to resist pesticides, so chemical control methods can become somewhat ineffectual when the same pesticide is used over a prolonged period. Spider mites, like hymenopterans and some

scale insect Scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient grouping than th ...

s, are haplodiploid and therefore arrhenotochous: females are

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respecti ...

and males are haploid. When mated, females avoid the fecundation of some eggs to produce males. Fertilized eggs produce diploid females. Unmated, unfertilized females still lay eggs that originate exclusively haploid males. To spread to new locations, they make use of ballooning for aerial dispersal.

Genera

The best known member of the group is '' Tetranychus urticae'', which has a cosmopolitan distribution, and attacks a wide range of plants, including peppers,

tomato The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word , ...

es,

potato The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae. Wild potato species can be found from the southern Un ...

es,

bean A bean is the seed of several plants in the family Fabaceae, which are used as vegetables for human or animal food. They can be cooked in many different ways, including boiling, frying, and baking, and are used in many traditional dishes t ...

corn Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn ( North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. ...

cannabis ''Cannabis'' () is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: '' Cannabis sativa'', '' C. indica'', and '' C. ruderalis''. Alternativel ...

, and

strawberries The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown Hybrid (biology), hybrid species of the genus ''Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The f ...

. Other species which can be important pests of commercial plants include ''

Panonychus ulmi ''Panonychus ulmi'', the European red mite, is a species of mite which is a major agricultural pest of fruit trees. It has a high reproductive rate, a short generation time (21 days at ) and produces many broods in a year, all of which contribute ...

'' (fruit tree red spider mite) and '' Panonychus citri'' (citrus red mite). The family is divided into these subfamilies,

tribes The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English is in the discipline of anthropology. This definition is contested, in part due to confl ...

and

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial ...

: ;Bryobinae Berlese *Bryobini Reck :*'' Neoschizonobiella'' Tseng :*'' Sinobryobia'' Ma ''et al.'' :*'' Marainobia'' Meyer :*''

Bryobia ''Bryobia'' is a genus of mites in the spider mite family, Tetranychidae. The taxonomy of the genus is difficult. The genus has been revised several times. It is difficult to distinguish these tiny species from each other on the basis of morphol ...

'' Koch :*'' Toronobia'' Meyer :*'' Pseudobryobia'' McGregor :*'' Strunkobia'' Livshitz & Mitrofanov :*'' Mezranobia'' Athias-Henriot :*'' Eremobryobia'' Strunkova & Mitrofanov :*'' Bryobiella'' Tuttle & Baker :*'' Hemibryobia'' Tuttle & Baker *Hystrichonychini Pritchard & Baker :*'' Bryocopsis'' Meyer :*'' Tetranychopsis'' Canestrini :*'' Notonychus'' Davis :*'' Dolichonobia'' Meyer :*'' Monoceronychus'' McGregor :*'' Mesobryobia'' Wainstein :*'' Hystrichonychus'' McGregor :*'' Parapetrobia'' Meyer & Rykev :*'' Peltanobia'' Meyer :*'' Tauriobia'' Livshitz & Mitrofanov :*'' Aplonobia'' Womersley :*'' Paraplonobia'' Wainstein :*'' Beerella'' Wainstein :*'' Magdalena'' Baker & Tuttle :*'' Porcupinychus'' Anwarullah :*'' Afronobia'' Meyer *Petrobiini Reck :*'' Neotrichobia'' Tuttle & Baker :*'' Schizonobiella'' Beer & Lang :*'' Schizonobia'' Womersley :*'' Dasyobia'' Strunkova :*'' Lindquistiella'' Mitrofanov :*''

Edella ''Edella'' is a genus of spider mites in the family Tetranychidae Spider mites are members of the Tetranychidae family, which includes about 1,200 species. They are part of the subclass Mite, Acari (mites). Spider mites generally live on the u ...

'' Meyer :*''

Petrobia ''Petrobia'' is a genus in Tetranychidae (spider mites), containing 34 described species. It includes some pest species. Description ''Petrobia'' mites can be recognised by their reddish-brown cuticle, dark body contents and the first leg pair ...

'' Murray ;Tetranychinae Berlese *Eurytetranychini Reck :*'' Atetranychus'' Tuttle ''et al.'' :*'' Synonychus'' Miller :*'' Eurytetranychus'' Oudemans :*'' Eurytetranychoides'' Reck :*''

Eutetranychus ''Eutetranychus'' is a genus of mites belonging to the family Tetranychidae. The genus has almost cosmopolitan distribution. Species: *'' Eutetranychus acaciae'' *''Eutetranychus africanus'' *'' Eutetranychus anitae'' *'' Eutetranychus bank ...

'' Banks :*'' Meyernychus'' Mitrofanov :*'' Aponychus'' Rimando :*'' Paraponychus'' Gonzalez & Flechtmann :*'' Sinotetranychus'' Ma & Yuan :*'' Anatetranychus'' Womersley :*'' Duplanychus'' Meyer *Tenuipalpoidini Pritchard & Baker :*'' Eonychus'' Gutierrez :*'' Crotonella'' Tuttle ''et al.'' :*'' Tenuipalpoides'' Reck & Bagdasarian :*'' Tenuipalponychus'' Channabasavanna & Lakkundi *Tetranychini Reck :*'' Brevinychus'' Meyer :*'' Sonotetranychus'' Tuttle ''et al.'' :*'' Mixonychus'' Meyer & Ryke :*'' Evertella'' Meyer :*'' Panonychus'' Yokoyama :*'' Allonychus'' Pritchard & Baker :*'' Schizotetranychus'' Trägårdh :*'' Yunonychus'' Ma & Gao :*'' Yezonychus'' Ehara :*'' Neotetranychus'' Trägårdh :*'' Acanthonychus'' Wang :*''

Mononychellus ''Mononychellus'' is a genus of mites belonging to the family Tetranychidae. The genus has almost cosmopolitan distribution. Species: *'' Mononychellus bondari'' *'' Mononychellus caribbeanae'' *'' Mononychellus chapalensis'' *'' Mononychel ...

'' Wainstein :*'' Platytetranychus'' Oudemans :*'' Eotetranychus'' Oudemans :*'' Palmanychus'' Baker & Tuttle :*'' Atrichoproctus'' Flechtmann :*'' Xinella'' Ma & Wang :*'' Oligonychus'' Berlese :*'' Hellenychus'' Gutierrez :*'' Tetranychus'' Dufour :*'' Amphitetranychus'' Oudemans

Countermeasures

Neem oil

Neem oil may provide control, when combined with a suitable surfactant and diluted with water. As with chemical control, repeated applications are required.

Predatory mites

Predatory mites of the

Phytoseiidae The Phytoseiidae are a family of mites which feed on thrips and other mite species. They are often used as a biological control agent for managing mite pests. Because of their usefulness as biological control agents, interest in Phytoseiidae has ...

family, including '' Phytoseiulus persimilis'', eat adult mites, their eggs, and all developmental stages between. Predatory mites can consume as many as 5 adult spider mites per day, or 20 eggs per day.

Insecticidal soap

Insecticidal soap spray is effective against spider mites. It is commercially available or can be made of certain types of household soap. However, since it will also kill predatory mites, its use is not recommended if the latter are present.

Harpin Alpha Beta

In some cases, the application of Harpin Alpha Beta protein may help in the treatment and prevention of infestation by stimulating the plant's natural defenses, restoring sap sugar levels and encouraging replacement of damaged tissues. This affects the spider mites' ability to down-regulate the immune response of a plant.

Acaricides

Acaricides are applied to crops to control spider mites. They can be either systemic or non-systemic in nature and can be persistent by providing residual activity for over a month. Drawbacks include high potential for development of

resistance Resistance may refer to: Arts, entertainment, and media Comics * Either of two similarly named but otherwise unrelated comic book series, both published by Wildstorm: ** ''Resistance'' (comics), based on the video game of the same title ** ''T ...

in mite populations, as has been observed in previous generations of miticides, and toxicity of some miticides towards fish. Thus proper selection, precautions and application are required to minimize risks.

Environmental conditions

Temporarily modifying environmental conditions has proven an effective method for insect pest control including spider mites. Generally dramatically decreased oxygen and increased carbon dioxide concentrations at elevated temperatures can lead to mortality at all developmental stages. However mild CO₂ enrichment has been shown to in fact increase mite reproduction. One study determined a concentration of 0.4% O₂ and 20% CO₂ gave a LT₉₉ (time to 99% mortality) of 113h at 20 °C and 15.5h at 40 °C. Another study reported 100% mortality of various stages of the two spotted spidermite using 60% CO₂ and 20% O₂ at 30 °C for 16h. Advantages would include decreased ability for resistance development compared to miticides and potential ease of application while drawbacks might include sensitivity of the plant to the conditions, feasibility of application, and human safety.

References

External links

* * * * {{Authority control Trombidiformes fi:Vihannespunkki