Interactive effects of temperature and substrates on selected life history parameters of the African palm weevil Rhynchophorus phoenicis (Fabricius) (Coleoptera: Curculionidae)

The African palm weevil Rhynchophorus phoenicis (Fabricius) is an alternative to conventional protein sources from livestock and poultry due to their rich nutritional content and ability to be reared on agricultural by-products. When establishing a production protocol for mass production of R. phoenicis larvae, it is imperative to understand the interaction between substrate and temperature on the development and reproductive success of the weevils. To determine the optimum temperatures for continuous production of R. phoenicis, the larvae were subjected to four temperatures (20 °C, 25 °C, 30 °C, and 35 °C) at a relative humidity of 70% on different substrates (elephant ear corm, peeled sugarcane, and palm yolk) in an incubator. The developmental duration of R. phoenicis larvae decreased with a temperature above 30 °C whilst percentage larval survival was high at 20 °C and 25 °C. The temperature with the fastest larval development and highest mortality was 35 °C. The optimal temperature from egg to the adult stage was observed at 25 °C. The oviposition and hatchability of eggs was high on elephant ear corm (EC), and palm yolk (PY) at 25 °C whilst the number of cocoons was high at 20 °C on decorticated coconut coir (DC). Thus, it is feasible to utilise the easily accessible substrates that interact well with temperature to produce optimum condition for the production of R. phoenicis larvae.