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Tetranychus urticae Koch,
Tetranychus telarius L., Tetranychus altheae Hanstein

Arachnida, Acari, Tetranychidae .

Glasshouse spider mite, Two spotted spider mite, Carmine spider mite

Description, Biology, Life Cycle, Damage, Common Names, Images

Two distinctive forms of glasshouse spider mite with two closely related biologies and producing the same damage occur:.
- yellow, more or less greenish form (*) ; this concerns 2 species T. urticae Koch and T. turkestani Ugarov and Nikolski (= T. atlanticus MacGregor), the latter not being generally found in glasshouses and being more meridional (*) ;.
- brick-red form: T. cinnabarinus Boisduval (*) (a distinct species for most UK taxonomists = carmine spider mite).
In autumn, individuals of a markedly orange colour, without any spots, which are the overwintering forms of T. urticae, occur.
- The adults have 2 typical dark spots on the back and 4 pairs of legs. The female is 0.5 mm long; the male is smaller and slender (0.3 mm long).
- Egg: spherical, less than 0.1 mm in diameter, smooth, whitish and translucent after the laying. The egg of T. cinnabarinus is mauve pink.
- Larva: of reduced size, it has 3 pairs of legs.

- Host plants: this mite is extremely polyphagous attacking almost 200 different hosts: wild plants, ornamentals, vegetable plants, fruit species. It is particularly damaging to vine, bean, cucumber, hop, cotton, clover, sunflower, fruit trees.
- Having overwintered, the females migrate to weeds and other herbaceous plants and, after a period of feeding, lay large number of eggs (*) ; fecundity: about a hundred eggs at a rate of 10 per day. The 2nd generation returns to vine and other cultivated plants in June.
At all the active instars glasshouse spider mite spins silken webs on the lower side of the leaves which retain humidity and ensure excellent protection against the wind, predators and pesticide treatments (*) .
To feed, the mite attacks the leaves and imbibes cellular sap (*) .
Its development is optimal between 23 and 30°C and at a relative humidity of less than 50%.
- Larval immature stages and nymphal development lasts 16 days at 20°C and 7 days at 31°C.

[R]Life Cycle
- 6 to 7 summer generations.
- The generations follow each other and the mite is found in vast numbers. The dissemination of the glasshouse spider mite takes place by the passage from one plant to another (if they touch each other), by ground over small distances, by transport on objects or people or by the wind, the silken thread acting as an aerophore.
At the end of summer, the orange form becomes predominant and will overwinter in various sheltered situations, including glasshouses.

- Direct damage is due to feeding punctures: the leaves become spotty, and then dry out (*) . If attacks are heavy, the plant may die.
- Also, the webs may constricte the plant and interfere with development. Such indirect damage is a particular problem in glasshouses where colonies of the mite may reach very high densities.

[R]Common Names
DE: Gemeine Spinnmilbe, Bohnenspinnmilbe, Hopfenspinnmilbe ES: Araña roja FR: Tétranyque tisserand, Acarien jaune IT: Ragnetto giallo dei giardini PT: ¦caro amarelo da vinha, Aranhiço amarelo GB: Glasshouse spider mite, Two spotted spider mite, Carmine spider mite

[R] Images

  1. Tetranychus urticae Koch (Coutin R. / OPIE)
    Severely damaged leaves of bean Webs that unite the various parts of the leaf and on which mites are present can be seen.
  2. Tetranychus urticae Koch (Coutin R. / OPIE)
    Affected leaf of eggplant Small white dots correspond to emptied cells.
  3. Tetranychus urticae Koch (Coutin R. / OPIE)
    Detailed picture of a silken web A few mites move on the web.
  4. Tetranychus urticae Koch (Coutin R. / OPIE)
    Adult Motile forms, spherical eggs as well as transparent exuviae can be seen (high magnification).
  5. Tetranychus urticae Koch (Cotton D. / INRA Montpellier)
    T. cinnabarinus Red form of T. urticae.
  6. Tetranychus urticae Koch (Cotton D. / INRA Montpellier)
    Females and eggs on leaf of maize
  7. Tetranychus urticae Koch (AGPM)
    Attack on maize
  8. Tetranychus urticae Koch (BASF)
    Attack on strawberry
  9. Tetranychus urticae Koch (Cotton D. / INRA Montpellier)
    Damage on strawberry
  10. Tetranychus urticae Koch (Cotton D. / INRA Montpellier)
    Female Very similar to T. urticae Koch.

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