Cost-benefit analysis of managing the Papuana uninodis (Coleoptera: Scarabaeidae) Taro beetle in Fiji

Taro (Colocasia esculenta (L.) Schott) plays a prominent role in the economies and cultures of Pacific Island countries such as Fiji. Unfortunately, taro is highly susceptible to invasion from taro beetles, which burrow into the corms and weaken the plants, rendering them unmarkable and prone to rot. Papuana uninodis Prell, an invasive alien species that is native to the Solomon Islands and Vanuatu, was first reported on Viti Levu (Fiji's largest island) in 1984. Since that time, taro production on Viti Levu has fallen substantially. In this paper, we employ data from surveys of households and communities to document the impacts of P. uninodis on Viti Levu. We then identify three management approaches-chemical controls, cultural controls, and switching from taro to another staple crop-and conduct a cost-benefit analysis of each. We find strong arguments for pursuing chemical control, which derives a net present value of monetised benefits of about FJ$139,500 per hectare over 50 yr, or >FJ$21 for each FJ$1 spent. Still, any of the three management options is more efficient than no management, even without any attempt to quantify the benefits to biodiversity or forest protection, underscoring the value of actively managing this invasive alien species.