Mites (inc)
Acarus, Lepidoglyphus and Tyrophagus spp.
Identification
The three species of mite most commonly found in UK grain stores are the grain mite Lepidoglyphus destructor, the flour mite Acarus siro, and Tyrophagus longior, and these often occur together. Mites are just visible to the naked eye (0.5 mm in length) and can be seen moving slowly on the surface of grain or associated produce. Under the microscope they are white/ translucent in appearance and with 8 legs (although the first larval stage has only 6 legs).
Symptoms
Mites feed on cereal germs (embryo part of the seed) and contaminate grain with allergens adversely affecting feed palatability.
Life-cycle
Mites can be found on the surface of bulks of grain, in spaces between grains and in dust and debris in most grain stores if the relative humidity is high enough. After hatching they pass through 1 larval stage and 2 nymphal stages before adulthood. Under ideal conditions this can be completed in 10-14 days. They thrive in warm, moist conditions (optimum relative humidity 80 % and optimum temperature 20 °C). Whilst mites are able to exist at very low temperatures they are unable to survive in dry environments due to desiccation (such as in grain with a MC of less than 14 %). At a grain MC of 16 °C and above they are considerably more successful.
Importance
Mite populations in grain stores can build up very quickly. Mites damage grain by feeding on the germ, tainting the produce with allergens and spreading fungal spores.
Management of storage pests
Clean stores thoroughly before harvest
Monitor grain heap surfaces for mite infestations
Reduce grain temperature to <5 °C and MC <14 °C
Turn the grain through a long conveying run which crushes the mites
Physically remove by running through a grain cleaning auger
Top dress stored grain with diatomaceous earth (DE) which can be incorporated into the surface of the grain heap. This contains absorbent silica which abrades the cuticles of insects and mites leading to desiccation and control
Fumigate using phosphine, methyl bromide or carbon dioxide (applied by specialist contractors)
