Description

Russet mites (Aculops lycopersici, Aculus lycopersici) are so small that a 14X hand lens is needed to see them. Because of their size, these mites are rarely noticed until plants are damaged. At this time, there may be hundreds of yellowish, conical-shaped mites on the green leaves immediately above bronzed leaves. Aceria lycorespici is the tomato erineum mite or Wolffentein mite and causes white and densely hairy patches on the stems and petioles. Tomato russet mite favours low humidity and high temperatures.  Each female produces 40-50 eggs every 2-3 days which hatch in 3 days. Mites live for about 80 days. Reproduction is completed in 12-15 days under protected cultivation. Tomato russet mites are half the size of spider mites (Tetranychus urticae and T. cinnabarinus).

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Damage

Tomato russet mites remove cell contents from leaves, stems, and fruit cells. Usually starting near the ground, infestations of this mite progress up the plant and lower leaves dry out, giving the plant an unhealthy appearance. The colour of the stems and leaves frequently becomes greasy bronze or russet. If not controlled, this pest can cause serious defoliation, particularly during hot weather, which results in sunburned fruit and crop loss.

Control

Look for bronzing on lower leaves and stems, then check damaged leaves and the green leaves immediately above them for mites. Damage is typically first observed when green fruit reaches 1 inch (5 cm); rarely is it first observed when more than 25% of the fruit are ripe. Try to determine the extent of each infested area in the field by examining leaves and stems for bronzing. Check these areas again in 2 or 3 days to see if they are increasing in size. Treatment is necessary immediately when damage symptoms begin to spread. The acceptable biological method of control are sulphur sprays.