Predaciousness Efficiency of Three Manure-Inhabiting Mite Species Against The Eggs of Callosobruchus Chinensis and Sitotroga Cerealella

Abstract

Individuals of three manure-inhabiting predaceous mite species were chosen to evaluate their efficiency as biological control agents against the eggs of two stored-product insects. The mite species were Cheyletus malaccensis (Acari: Cheyletidae), Macrocheles robustulus (Acari: Macrochelidae) and Gamasholaspis variabilis (Acari: Parholaspididae). Meanwhile, the tested insects were Sitotroga cerealella (Lepidoptera: Gelechiidae), and Callosbruchus chiensis (Coleoptera: Bruchidae). For each insect, twenty eggs were exposed to five individuals of the predaceous mite. The eggs and mites were kept in a dark room in the laboratory. After treatment, inspections were performed 24, 48 and 72 hrs later. In most inspection intervals, the average percentages of the consumed eggs by these predaceous mite species were significantly different from those of control. All three mite species consumed a lot of eggs, especially after 72-hour post treatment. The average percentages of consumed S. cerealella eggs by either mite species were always higher than the average percentages of C. chinensis eggs consumed by the same mite species. Macrocheles robustulus was found to be the most effective predator against both insects' eggs where the average percentages of S. cerealella and C. chinensis consumed eggs after 72 hrs were 91.67 and 53.33%, respectively. Gamasholaspis variabilis was found to be the least effective predator against the eggs of both insects where the average percentages of the consumed eggs of S. cerealella and C. chinensis after 72 hrs were 86.67% and 38.33%, respectively. The consumption of the eggs of each of the two targeted insects by the individuals of the three evaluated mite species increased as the exposure time increased. Cannibalism between the individuals of each of the three valuated mites wasn't observed while performing the experiment.