Effect of irradiation and insect pest control on rots and sensory quality of two varieties of stored ware white yams in Ghana

Abstract

The coffee bean weevil, Araecerus fasciculatus Degeer (Coleoptera: Curculionidae) is associated with rots in stored yam tubers. The current study was designed to assess the effect of irradiation and other insect pest control strategies on rots and sensory quality of stored yams. 450 tubers each of two varieties of white yam (Dioscorea rotundata Poir) namely ‘Puna’ and ‘Asana’ were divided into two groups with half irradiated and the other half not irradiated. The two groups were then further divided into three sub-groups. The first sub-group was treated with a chemical insecticide ‘Superguard’ (400g/l Pirimiphos-methyl and 75 g/l Permethrin) against A. fasciculatus infestation whilst the second sub-group was placed in insect-proof boxes with no chemical treatment. The third sub-group was neither chemically treated nor placed in insect-proof boxes. They were all then stored in improved yam barns for four months after curing in February. Sprouts that developed on the non-irradiated tubers were broken off weekly. They were examined for rots and weight loss over the storage period. Sensory evaluation was conducted on the tubers at the end of storage to determine whether the treatments affected their sensory quality. It was observed that the irradiation and chemical insecticide treatments did not have significant effect (p>0.05) on percent rots and weight loss while the effect of storage on these parameters was significant (P<0.05). Generally, percent rots increased while tuber weights reduced over the storage period. Freshness of the whole tubers and cooked texture were significantly (P<0.05) improved by irradiation.