Variation in substrate nutritional composition and its effects on the growth, development, and nutrient composition of Rhynchophorus phoenicis Fabricius (Coleoptera: Curculionidae)

Consumption of African Palm Weevil larvae is a potential solution to the escalating need for protein in Ghana. Currently, insect farmers rely heavily on agricultural by-products, for their production. However, the changes in nutritional content of these substrates over the duration of the larval stage is not well understood as its decline could have a negative effect on the larval development. The palm weevil larvae were reared on eleven (11) substrates and the changes in the nutrient content of the substrates over time during the larval rearing duration, and their effect on larval survival, larval duration and larval weight were assessed. The substrates tested included cocoyam cake, spoilt onion, banana corm, spoilt garden eggs, coconut coir, cocoa pod, raphia palm, elephant ear corm, sliced false yam, sugarcane and palm yolk. The substrate samples were collected weekly from the first to the fourth week and analysed for crude fat, crude protein, ash and carbohydrate contents. The nutritional content of all the substrates did not differ in the first week. However, crude protein, crude fat and carbohydrate significantly differed in the second, third, and fourth weeks. Larval survival, larval duration and weight of larvae were significantly affected by the changes in the nutrient content of the substrates in the second, third and fourth weeks. The results showed that elephant ear corm, sliced false yam and palm yolk have necessary nutritional requirements to sustain the larvae during development.