Cowpea storage: Can small farmers use polyethylene terephthalate bottles and wood ash as an alternative to avoid damage caused by Callosobruchus maculatus?

The aim of this study was to investigate the effectiveness of the combination of Polyethylene terephthalate (PET) bottles and ash in controlling Csllosobruchus maculatus and maintaining the quality of grains of cowpea cultivars. The following storage structures were used: PET bottle in airtight conditions and glass jars in non-airtight condition (control). The wood ash used in this research came from the burning process of eucalyptus (Eucalyptus grandis) wood. The experiment was carried out in a 2 × 2 × 4 factorial scheme, with two cowpea cultivars (BRS Tumucumaque and BRS Guariba), two forms of storage (PET bottle – airtight and glass jars – non-airtight) and four doses of eucalyptus wood ash (0.0; 1.0; 2.0 and 4.0 kg t⁻¹), in a completely randomized design with three replications. Each plot contained 500 g of cowpea. The effectiveness of treatments was measured by the instantaneous population growth rate (r_i) of C. maculatus. In r_i, 35 adult, non-sexed insects were used. Adult progenies were counted after 60 days of storage. For qualitative grain evaluation the following characteristics were analyzed: water content, germination, apparent specific mass and electrical conductivity. The results obtained in this study confirm for the first time that the combined use of PET and ash do not affect grain quality and it is efficient in the management of C. maculatus in cowpea cultivars. In the present study, a significant reduction in the emergence of C. maculatus was observed in the BRS Tumucumaque, making it possible that this cultivar has some potential for resistance to bruchid.