Morphological and Molecular Identification of Sitophilus Species (Coleoptera: Curculionidae) Infesting Stored Cereal Grains

Abstract

Morphological and molecular identification of Sitophilus species (Coleoptera: Curculionidae) infesting stored cereal grains was carried out to determine species composition, distribution, and genetic relationships among stored-product pest populations. Infested grain samples were collected from storage facilities showing characteristic damage such as grain perforation, powdering, and reduced seed viability. Adult weevils were examined using standard morphological keys based on rostrum structure, elytral punctation, and genital characteristics to differentiate Sitophilus species. Molecular identification was performed using PCR amplification and sequencing of mitochondrial COI gene fragments, enabling accurate species confirmation and assessment of genetic variation. Results revealed the presence of multiple Sitophilus species, with S. oryzae, S. zeamais, and S. granarius being the most frequently encountered across storage systems. Phylogenetic analysis showed clear genetic clustering corresponding to species-level differentiation, with low intraspecific but distinct interspecific variation. The integration of morphological and molecular data improved diagnostic accuracy, particularly in cases of overlapping morphological traits. Infestation intensity varied among storage conditions, with higher pest abundance observed in poorly managed and high-moisture grain environments. The study highlights the importance of precise species identification for effective stored-grain pest management. These findings support the development of targeted integrated pest management strategies, including improved storage hygiene, monitoring systems, and preventive control measures to reduce losses caused by Sitophilus spp. in cereal grain storage systems.