Natural occurrence of fungal species on the rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae), in Punjab, Pakistan

The rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), is one of the major insect pests of stored wheat, maize, rice and cereal-based food products worldwide. Besides direct damages to stored food, S. oryzae has the ability to act as a vector of several fungal pathogens. Here, we collected strains of S. oryzae from rice storage facilities in Punjab, Pakistan, during 2020-22 and quantified fungal species on the bodies of weevils. A total of 54 isolates consisting of 17 species belonging to 10 genera were identified and morphologically characterized from different strains of S. oryzae. Overall, Aspergillus spp. were the most frequent (52%) in all the isolates followed by Alternaria spp. (13%), Metarhizium spp. (9%), Penicillium spp. (7%), Cladosporium sp. (5%), Rhizopus sp. (4%), Verticillium sp. (4%), Trichoderma sp. (2%) and Fusarium sp. (2%). The occurrence frequency of different fungal species was as follows: Aspergillus nidulans (7%), Aspergillus fumigatus (7%), Aspergillus flavus (15%), Aspergillus parasiticus (15%), Aspergillus oryzae (7%), Alternaria alternata (9%), Alternaria tenuissima (4%), Cladosporium cladosporioides (6%), Metarhizium flavoviride (4%), Metarhizium anisopliae (6%), Mucor racemosus (2%), Penicillium expansum (4%), Penicillium citrinum (4%), Rhizopus oryzae (4%), Verticillium lecanii (4%), Trichoderma harzianum (2%), and Fusarium oxysporum (2%). The Chi-square test of association revealed non-significant association of fungal species with different localities (p > 0.05). In conclusion, the results of the present study revealed that S. oryzae could play an important role in spreading and promoting fungal contamination and subsequent production of mycotoxins in stored foodstuff.