Diversity of insect pests of common bean and pigeon pea in the Republic of Congo revealed by DNA barcoding

Abstract

In Central Africa, the development of leguminous crops is accompanied by a proliferation of pests, such as seed-beetles (Coleoptera: Chrysomelidae: Bruchinae). Integrated biological control against insect pests requires a preliminary phase of early detection and monitoring of potential invasive species, which is often limited by the availability of diagnostic morphological characteristics. DNA barcoding represents a powerful molecular tool for identifying specimens, and the mitochondrial sequences produced can provide information concerning the origins of introduced species. In this study, we characterised the diversity of insect pests present in farmer storage sites and plots of common bean and pigeon pea, by using DNA barcoding of specimens sampled in the five main agricultural regions of the Republic of Congo. The cosmopolitan seed-beetle species Acanthoscelides obtectus (Say, 1831) (Coleoptera: Chrysomelidae: Bruchinae) was recognised as the major pest sampled on common bean. The sub-Saharan species Specularius erythraeus (Pic, 1908) (Coleoptera: Chrysomelidae: Bruchinae) was the main species found in pigeon pea plots, sometimes co-occurring with the cosmopolitan species Callosobruchus maculatus (Fabricius, 1775) (Coleoptera: Chrysomelidae: Bruchinae). A fourth bruchine, Zabrotes subfasciatus (Boheman, 1833), a weevil species of the genus Apion Herbst, 1797 (Coleoptera: Brentidae) and two moth species were also identified: a species of the genus Mussidia Ragonot, 1888 (Pyralidae) and the cosmopolitan pest of stored food, Cadra cautella (Walker, 1863) (Pyralidae). These results differ from species lists compiled in the 1980s, thus providing updated knowledge concerning the pest species present in this region and fundamental information for choosing appropriate methods of control.