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

Acari Mites are small arachnids (eight-legged arthropods) of two large orders, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. However, most recent genetic analyses do not recover the two as ea ...

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

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

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

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

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 A colony is a territory subject to a form of foreign rule, which rules the territory and its indigenous peoples separated from the foreign rulers, the colonizer, and their ''metropole'' (or "mother country"). This separated rule was often orga ...

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

hymenoptera Hymenoptera is a large order of insects, comprising the sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are parasitic. Females typi ...

ns and some

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

s, are

haplodiploid Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy is sometimes called arrhenotoky. Haplodiploidy determines the se ...

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. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...

and males are

haploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Here ''sets of chromosomes'' refers to the num ...

. When mated, females avoid the

fecundation Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or of ...

of some eggs to produce males. Fertilized eggs produce diploid females. Unmated, unfertilized females still lay eggs that originate exclusively

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 In biogeography, a cosmopolitan distribution is the range of a taxon that extends across most or all of the surface of the Earth, in appropriate habitats; most cosmopolitan species are known to be highly adaptable to a range of climatic and en ...

, and attacks a wide range of plants, including peppers,

tomato The tomato (, ), ''Solanum lycopersicum'', is a plant whose fruit is an edible Berry (botany), berry that is eaten as a vegetable. The tomato is a member of the nightshade family that includes tobacco, potato, and chili peppers. It originate ...

es,

potato The potato () is a starchy tuberous vegetable native to the Americas that is consumed as a staple food in many parts of the world. Potatoes are underground stem tubers of the plant ''Solanum tuberosum'', a perennial in the nightshade famil ...

es,

bean A bean is the seed of some plants in the legume family (Fabaceae) used as a vegetable for human consumption or animal feed. The seeds are often preserved through drying (a ''pulse''), but fresh beans are also sold. Dried beans are traditi ...

corn Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout Poaceae, grass that produces cereal grain. It was domesticated by indigenous peoples of Mexico, indigenous peoples in southern Mexico about 9,000 years ago ...

cannabis ''Cannabis'' () is a genus of flowering plants in the family Cannabaceae that is widely accepted as being indigenous to and originating from the continent of Asia. However, the number of species is disputed, with as many as three species be ...

, and

strawberries The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid plant cultivated worldwide for its fruit. The genus ''Fragaria'', the strawberries, is in the rose family, Rosaceae. The fruit is appreciated f ...

. Other species which can be important pests of commercial plants include '' Panonychus ulmi'' (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 use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

and

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

: ;Bryobinae Berlese *Bryobini Reck :*'' Neoschizonobiella'' Tseng :*'' Sinobryobia'' Ma ''et al.'' :*'' Marainobia'' Meyer :*'' Bryobia'' 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'' Meyer :*'' Petrobia'' Murray ;Tetranychinae Berlese *Eurytetranychini Reck :*'' Atetranychus'' Tuttle ''et al.'' :*'' Synonychus'' Miller :*'' Eurytetranychus'' Oudemans :*'' Eurytetranychoides'' Reck :*'' Eutetranychus'' 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'' Wainstein :*'' Platytetranychus'' Oudemans :*'' Eotetranychus'' Oudemans :*'' Palmanychus'' Baker & Tuttle :*'' Atrichoproctus'' Flechtmann :*'' Xinella'' Ma & Wang :*'' Oligonychus'' Berlese :*'' Hellenychus'' Gutierrez :*'' Tetranychus'' Dufour :*'' Amphitetranychus'' Oudemans

Countermeasures

Predatory mites

Predatory mites of the family Phytoseiidae, 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.

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 Acaricides are pesticides that kill members of the arachnid subclass ''Acari'', which includes ticks and mites. Acaricides are used both in medicine and agriculture, although the desired selective toxicity differs between the two fields. Termino ...

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 resurgence and resistance 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