Effects of Larger grain borer Prostephanus truncatus (Coleoptera: Bostrichidae) on nutrient content of dried staple roots and tubers

The effect of infestation and damage by Larger grain borer (LGB), Prostephanus truncatus (Horns) (Coleoptera: Bostrichidae) on nutrient content of some dried processed root and tuber crops (cassava, yam, sweet potato and cocoyam) were investigated in the laboratory at 25-30 ºC and 70-90% R.H. Thirty five grams each of the chips from two varieties of sweet potato, cassava, cocoyam and a variety of yam were separately placed in a 950 ml sized glass jar. The Test Host Crops (THC) were artificially infested with one, two and three pairs of adult LGB. The experiment was conducted using a completely randomized design with each treatment replicated three times and kept for 90 days. Data were taken on final population of adult LGB, weight of powder and percentage weight loss. Data on proximate analysis of LGB-infested THC after 90 days was also collected. The response of roots and tubers to infestation by LGB on the THC was significantly different. Percentage loss in quantity of root and tuber crops after 90 days of infestation showed that THC infested with two pairs of the insect had higher weight loss of the crops. The THC infested with two pairs of LGB had higher moisture content and least crude protein was recorded on the THC infested with one pair of LGB while the ones infested with three pairs of LGB had higher crude fat content. Uninfested THC had higher carbohydrate content. The findings of this study show that LGB is a serious threat to stored roots and tubers and to food security. The nutritional value of root and tuber crops was adversely affected by infestation of LGB in storage.