Susceptibility of ten rice brands to weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), and their influence on the insect and infestation rate

BACKGROUND: Susceptibility studies keep farmers, managers and household users informed and enhance breeding program’s testing against infestation and damage by storage insect pests. Therefore, laboratory tests were carried out to examine the susceptibility of ten rice brands to rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), infestation under temperature and relative humidity of 25 ± 2 °C and 75 ± 5%, respectively. The specific objectives of the study were to identify some commercially available rice brands with resistance to S. oryzae, by determining whether brand difference influences insect body weight at emergence and whether infestation is related to brand palatability and appearance. The ten brands used for the study were royale stallion, Mama royale, parboiled rice, Mama gold, white rice, Super eagle, Indian rice, champion rice, Abakiliki rice and Mama Africa, and standard methods were used to achieve the objectives. The indices measured were F(1) progeny emergence, grain weight loss and frass accumulation. RESULTS: The results showed that Abakiliki rice was poor in both palatability and appearance, whereas Super eagle was the most palatable and white rice was visually excellent. The results further showed that no brand was resistant to infestation and damage by S. oryzae. Males that were bred on the different rice brands did not differ in weight at emergence, but the weight of females at emergence was influenced by brand difference, and this suggests that female insects are more sensitive to brand difference at weight gain. CONCLUSION: Palatability and appearance were important in the susceptibility of rice brands to S. oryzae. The proliferation of diverse genotypes of rice (branded) with enhanced resistance to S. oryzae should be strongly encouraged to reduce susceptibility and increase rice security.