Arachnida, Acari, Tetranychidae .
Description, Biology, Life Cycle, Damage, Common Names, Images
- Host plants: vine as well as fruit trees such as apple, pear, cherry, the currant.
- Adult: the females live 12 to 18 days and lay 24 to 48 eggs in 10 days.
- Egg: embryonic development lasts 5 to 17 days according to the temperature. The fruit tree red spider mite winters in the egg stage. The winter eggs are laid on vine level with the knots, on old wood and on the vinestock. They are deposited on fruit trees at the base of the current year's twigs and especially on old wood, at the insertion points of the branches, in the scars and around the buds and in depressions. When present in large numbers, they may form reddish plates. The summer eggs are laid on the leaves.
- Immature stages: the young larva originating from the winter egg moves to the leaves on which it develops. Development comprises 3 mobile instars 'one larval, two nymphal) separated by inactive instars. The development period varies from 7 to 12 days according to the temperature.
- The mobile forms feed by sucking the sap of the parenchyma cells of the underside of the leaves, having punctured them with the aid of their stylet-like mouthparts (*) .
- The hatching of the winter eggs begins in April and it duration depends on the spring temperature. Depending on the regions, 5 to 8 generations follow each other without interruption until the end of the summer.
- The lrngth of the life-cycle depends on the temperature and on the humidity (optimum 23 to 25°C and relative humidity 50 to 70%). A high temperature and a low humidity kill the eggs and may interrupt the multiplication of the mite.
- The highest population density is observed in July-August. The laying of winter eggs begins in mid-August but at times earlier in case of heavy infestation.
- Damage may be considerable. vine and fruit tree leaves turn yellow, brown and become characteristically leaden in appearence (*) ; they may drop prematurely. Feeding damage reduces photosynthesis and causes a loss of water. On vine, the quality and quantity of the harvest are reduced (*) .
- In spring, the larvae and nymphs originating from winter eggs may congregate, causing a brittling and deformation of the shoots on which they settle. When on the vine, the anlage of bunches of grapes end up by being more or less destroyed.
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