Beyond nectar provision: The other resource requirements of parasitoid biological control agents

Abstract

Recent work in natural enemy nutrition has generated dramatic results, ranging from parasitoid longevity increasing several-fold when appropriate nectar is made available to detailed quantification of changes in parasitoid searching behaviour and 'giving-up times' when they have nectar access. This floral-resource-based approach to enhancing biological control of pests has also led to many outcomes and is currently operating in a wider context: that of on-farm ecosystem services. Some recent publications have demonstrated that the provision of nectar resource subsidies within and around crops can positively impact a number of other ecosystem services, ranging from pollination to aesthetics, and benefit eco-marketing. However, adult food is not the only resource requirement of parasitoids. Many species require alternative hosts, overwintering habitat, protection from tillage, and refuge from adverse biotic and abiotic conditions. Also, recent work has emphasised the importance of considering spatial and temporal scales when manipulating agro-ecosystems in favour of beneficial insects and the impact that climate change may make on future host-parasitoid dynamics. This review summarises recent work on these additional requirements of parasitoids with the aim of promoting the integration of the floral resource subsidies into a more ecosystem-based view of pest suppression by parasitoids.