Petrobia latens Miiller Stone mite

This widespread but minor pest is associated mainly with members of the Poaceae and, if numerous, will cause damage to various crops, including carrot, lettuce and onion. Symptoms range from a yellow speckling of leaves to a general bronzing; also, the foliage often becomes shrivelled and brittle. Attacks, which tend to develop in patches, are most often noted under dry conditions; the symptoms caused appear similar to the effects of drought. The mites do not produce webbing.


Eggs are laid during the summer on stones, clods of soil and other non-plant surfaces, usually in the vicinity of host plants. Diapausing eggs remain in situ for extended periods during hot, dry conditions before hatching. Non-diapausing eggs, however, hatch in approximately 1-2 weeks, and the initially bright red immature stages feed for a similar period before becoming adults. This species is parthenogenetic and motile stages occur throughout the year.


Adult female brown and broadly pear-shaped, tapering posteriorly; legs very long, especially the first pair, and relatively narrow; body setae simple (cf. clover bryobia mite, Bryobia praetiosa, p. 265). Egg more or less spherical and shiny, either white (a diapausing egg) or bright red (a non-diapausing egg); the latter has a distinctly ribbed cap.

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