Competition between Two Species of the Genus <i>Sitophilus</i> (Coleoptera: Curculionidae) on Wheat and Barley

Abstract

Species can coexist and infest stored products at different population densities. We evaluated the population growth of Sitophilus oryzae (L.) and Sitophilus granarius (L.) (Coleoptera: Curculionidae) on wheat and barley in laboratory conditions. Ten adults of each species were placed in vials containing wheat or barley alone or in combination, and the number of adults was counted after 65 and 120 days. These tests were performed at 25 and 30 °C. Moreover, the number of damaged grain kernels and the weight of frass produced were also recorded. In general, the simultaneous presence of both species had a negative effect on the population growth of either S. oryzae or S. granarius. Nevertheless, no significant differences were noted regarding the number of damaged kernels and the weight of frass in most of the combinations tested. Moreover, the temperature seems to have a negative effect if both species were combined, especially at 30 °C. Our results showed that there was competition in the progeny production capacity when both species were together, but this competition was temperature and commodity-mediated.

Keywords

• rice weevil
• granary weevil
• population growth
• frass
• damaged kernels
• wheat