Uninvited guests: New stored mangrove rice insect pests in Guinea-Bissau

Abstract

Mangrove swamp rice is vital for food security in Guinea-Bissau, yet insect infestations cause significant post-harvest losses worldwide. This study identified insect pests affecting stored rice seeds using both morphological identification and DNA barcoding. In 2022, 64 rice samples were collected from 13 villages across 3 coastal regions yielding 1504 insect specimens, classified into 13 morphotypes from Coleoptera, Lepidoptera, and Hemiptera orders. DNA barcoding confirmed the identity of six species, including global primary rice pests Sitophilus oryzae Hustache, 1930, Rhyzopertha dominica (Fabricius, 1792), and Sitotroga cerealella (Olivier, 1789), and the secondary pests Tribolium castaneum (Herbst, 1797) and Cryptolests pusillus (Schénherr, 1817). This is the first record of these taxa in mangrove swamp rice seeds in West Africa. Four species are reported for the first time to Guinea-Bissau: S. oryzae, C. pusillus, Platymetopus vestitus Dejean, 1829 (Coleoptera), and S. cerealella (Lepidoptera). Among these, R. dominica had the highest relative abundance (68%), while S. oryzae appeared in all regions. Rhyzopertha dominica and S. cerealella were prevalent in Cacheu and Oio. Their widespread presence across Africa suggests a broader distribution. Effective management strategies include hermetic storage, cleaning, biological control, and efficient drying techniques. This study holds significant importance as it presents findings related to the under-researched African rice species (Oryza glaberrima) and a specialized cultivation system: mangrove swamp rice. Findings offer valuable insights into storage practices to enhance food security in rice-producing regions and pave the way for future research on pest management and sustainable rice storage solutions.