Plant derived powders as alternatives for Sitophilus oryzae L. (Coleoptera: Curculionidae) control in stored maize grains

Abstract

Maize is the major staple food in Africa. In developing countries, post-harvest losses due to insect pests are up to 40% of total production. Inert  powders can be alternative tools in integrated pest management programs of stored cereals. The aim of this study was to assess the efficacy of ashes from cashew (Anacardium occidentale) branches, charcoal powder, dried and milled Eucalyptus citriodora leaves, and diatomaceous earth  (standard check), for Sitophilus oryzae control on stored maize grains. The experimental design was completely randomized with 11 treatments and 4 replications. Insect introduction was carried out immediately after treatment application and at 30 and 60 days after. The mortality assessment was performed by counting the dead insects at 10 and 20 days after each infestation. The emergence of S. oryzae adults was also assessed at three different times. The germination of treated grains was also evaluated. Data analysis was performed on the SISVAR statistical package. Diatomaceous earth showed maximum control efficiency (73.75%) at 10-day evaluation, reaching total control at a 20-day evaluation. The remaining treatment control efficiency was below 50% in all concentrations and evaluations. The lowest insect emergence rates were observed in grains treated with diatomaceous earth or charcoal powder, which were more efficient than cashew ashes, Eucalyptus citriodora, and untreated control. There was no  significant effect of the tested products on seed germination so, they can be used in smallholder farmers' grain storage. The results allow us to affirm that Eucalyptus citriodora charcoal powder, and cashew ashes can be used to reduce Sitophilus oryzae damage in traditional agricultural systems. Considering the reduction in the Sitophilus oryzae progeny, the potential use of charcoal powder should be considered, given the efficiency compared to that of the diatomaceous earth. Thus, the plant-derived products tested in this study has the potential to be used in the integrated management of Sitophilus oryzae in stored products.

Key words: Ash, Charcoal, Diatomaceous earth, inert, dust, maize, storage, pest