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 evid ...

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

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

of plants, where they may spin protective silk webs, and they can cause damage by puncturing the plant

cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

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 Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

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 '' metropolitan state'' ...

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 the ...

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 sex ...

and therefore arrhenotochous: females are diploid and males are haploid. 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 new individual organism or offspring and initiate its development. Proce ...

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 Ballooning may refer to: * Hot air ballooning * Balloon (aeronautics) * Ballooning (spider) * Ballooning degeneration, a disease * Memory ballooning See also * Balloon (disambiguation) A balloon is a flexible container for (partially or fully) ...

for aerial dispersal.

Genera

The best known member of the group is '' Tetranychus urticae'', which has a

cosmopolitan distribution In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in appropriate habitats. Such a taxon, usually a species, is said to exhibit cosmopolitanism or cosmopolitism. The ext ...

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

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 thr ...

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. The ...

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. 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 and genera: ;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

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 ''Phytoseiulus'' is a genus of mites in the Phytoseiidae family. A predatory mite, this is the mite predator most frequently used to control two-spotted spider mites in greenhouses and outdoor crops grown in mild environments. This mite was ac ...

'', 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 Insecticidal soap is used to control many plant insect pests. Soap has been used for more than 200 years as an insect control. Because insecticidal soap works on direct contact with pests via the disruption of cell membranes when the insect is pen ...

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 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 Systemic fundamental to a predominant social, economic, or political practice. This refers to: In medicine In medicine, ''systemic'' means affecting the whole body, or at least multiple organ systems. It is in contrast with ''topical'' or ''loc ...

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 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