Tyrophagus longior Gervais Grainstack mite

This widely distributed pest, sometimes known as French 'fly', is often abundant in straw and undecomposed horse manure; infestations frequently develop on cucumber plants grown on straw bales or raised by traditional manure culture. The mites are also associated with various stored products and may occur as secondary invaders on bulbs and corms that have gone mouldy during storage. When swarming upon cucumber plants, the mites produce minute holes in the young leaves; they also cause shoot distortion and, sometimes, blindness.


The mites breed continuously under favourable conditions and the life-cycle (from egg through one larval and two nymphal stages to adult) takes from 2 to 4 weeks, depending upon temperature. Infestations in straw bales and manure in cucumber beds often spread to the plants; the mites often hide within the shelter of the unfurling leaves, and feeding on cucumber plants is usually restricted to the young foliage and growing points. Although the mites may deposit eggs on infested cucumber plants, such sites appear to be unfavourable for breeding success and, in the absence of straw within which to overwinter, mite numbers decline.


Adult 0.3-0.7 mm long, shiny, whitish, with very long bristle-like setae on the body (see Fig. 176); legs pale brown. Egg 0.1mm long, oval, hyaline-whitish, with a sculptured surface.

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