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a family of mites of the order Acariformes of the class Arachnoidea. Tetranychidae are plant parasites, damaging leaves and stems by weaving silk tents around them. The mites reach a length of 0.5 mm. The coloration is yellow-green; wintering females are red. The chitin is soft and translucent and bears slender setae. The mouth is suctorial. A pair of stylets are used to pierce the surface of the leaf and suck out the contents of the cells. The salivary glands produce a secretion that destroys chloroplasts, leading to destruction of the plant when there is extensive mite infestation. Tetranychidae infestation is greatest when a plant is at the peak of its developmental cycle. As leaf fall begins, the female Tetranychidae leave for hibernation. In southern regions there may be as many as 32 generations each year. Each day the female deposits as many as ten orange and slightly flattened eggs, which are attached to the silk web by a stalk.
In the USSR, approximately 100 species of Tetranychidae are encountered. Many species are destructive pests of agricultural crops. They damage both herbaceous and woody plants. By sucking out the juices from cells and destroying the chloroplasts, the mites cause the formation of red spots on the leaves. The spots merge, and the leaves then turn brown, wither, and fall prematurely.
The common spider mite (Tetranychus telarius, or T. urticae) is found throughout the world. It severely damages cotton, gourds, soybeans, and—in greenhouses—cucumbers. The common spider mite infests plants from June through August. There are as many as 24 generations per year. T. atlanticus, which morphologically resembles the common spider mite, has been encountered in the USA, Bulgaria, Yugoslavia, Turkey, Japan, and the USSR. It damages cotton, alfalfa, clover, strawberries, pears, apples, and several other crops. T. viennensis is distributed mainly in the southern fruit-raising regions of the USSR. It feeds primarily on plants of the family Rosaceae; in the second half of the summer it is particularly destructive to apple, plum, and cherry trees. There are seven to nine generations each year. Panonychus citri is found in subtropical regions of the USSR, where it damages citrus, mulberry, and cherry laurel trees. It reproduces most intensely on lemon and Trifolium. There are ten generations per year.
The principal control measure is spraying plants with acaricides. In greenhouses biological control is used: such predatory acarines as Phytoseiulus persimilis are raised and released.
REFERENCERekk, G. F. Opredelitel’ tetranikhovykh kleshchei. Tbilisi, 1959.
E. M. BULANOVA-ZAKHVATKINA