Biological control
Cheyletus eruditus has been collected from many countries around the world. © H Taylor
Cheyletus eruditus is the only biological control agent used to control pest mites in food storage systems, for example, in grain and seed stores.
It is mainly used to target:
- Acarus siro - flour mite - Astigmata: Acaridae, and, to a lesser extent
- Lepidoglyphus destructor - grocers’ itch mite - Astigmata: Glycyphagidae
As well as contaminating and damaging the food product, both species can cause allergic reactions in humans and domesticated animals in contact with infested material.
The abilities of C. eruditus to survive long periods of starvation and to exploit alternative prey (including other members of its own species) are good biocontrol qualities. Also, because it is parthenogenetic, a few females can maintain the population when prey is in short supply and respond to subsequent increases in pest numbers.
Mass rearing techniques have been developed which have enabled populations to be produced for commercial use. C.eruditus mites tend to be released into empty stores to control leftover pest mites in preparation for restocking.
Relative humidity is the main influence on the level of control achieved by C. eruditus.
- in winter, high humidity enables pest mites to reproduce at a faster rate than their predator, and biocontrol is, therefore, ineffective
- humidity levels in summer, however, are more favourable to C. eruditus and it is able to reduce pest numbers
At high levels of infestation, chemical control is used to suppress pest populations before introducing C. eruditus. The effectiveness of this integrated approach is increased by rearing strains of the predator with low susceptibility to the pesticides used (Gause et al.,1936; Zdárková, 1986, 1997; Zdárková and Horak, 1990; Gerson et al., 2003).