Distribution of Arthropods in Rice Grains in Malaysia

Objective: To determine distribution of arthropods in rice grains obtained from different sources. Methods: Rice samples were randomly collected from public in urban areas, farmers in rice field areas, aborigines in undeveloped areas and retailers in commercial premises. Random samples of rice were taken out from each sample for isolation of arthropods using a modified Berlese Tullgren Funnel Method. Mites were mounted prior to identification; weevils were directly identified. Results: Samples of rice from retailers in commercial premises had the highest infestation by arthropods followed by samples from urbanites, aborigines and rice farmers. Two species of weevils, Sitophilus oryzae (S. oryzae) and Sitophilus granarius (S. granarius), were found. Samples from commercial premises had the least percentage of weevils compared to those collected from domestic premises. Depending on the source of samples, densities of S. granarius and S. oryzae ranges from 11-103 weevils/kg and 7-80 weevils/kg, respectively. Important species of mites in stored rice identified were mainly members of the families Cheyletidae, Echimyopodidae, Pyroglyphidae, Saproglyphidae and Tenuipalpidae. Among the species of mites identified were Austroglycyphagus malaysiensis, Cheyletus fortis, Cheyletus malaccensis, Dermatophagoides pteronyssinus, Gramrnolichus malukuensis and Suidasia pontfica. Average density of most of the mites was less than 40 mites/kg of rice grains. In this study, the highest number of mites in rice samples was recovered from commercial premises, followed by samples from urbanites. Samples from farmers and aborigines contained lesser mites. Conclusion: This study demonstrated the presence of 3 allergenic mite species in rice, i. e A. malaysiensis, D. pteronyssinus and S. pontifica. Weevils, S. oryzae and S. granarius that are known to be allergenic, were also found.