5 The Parasitoids’ Need for Sweets: Sugars in

Mass Rearing and Biological Control

F.L. Wäckers*

Laboratory of Entomology, PO Box 8031, 6700 EH Wageningen, The Netherlands

Introduction

Due to their ability to regulate herbivore
populations, parasitoids and predators play
an important role both as biological control
agents and as keystone species in natural
ecosystems. Given this fact, it is not surpris-
ing that research interest has largely focused
on how predators and parasitoids find and
interact with their herbivorous prey/host
(Godfray, 1994; Dicke and Vet, 1998).
However, the majority of these principally
carnivorous arthropods also use plant-
derived foods as a source of nutrients. This

vegetarian side of the menu may include

various plant substrates, such as nectar, food

bodies, pollen and fruits, as well as foods

indirectly derived from plants (e.g. honey-

dew, or pycnial fluid of fungi). In some cases,

predators may also feed on plant productive

tissue, in which case they have to be classi-

fied as potential herbivores (Coll, 1996). The

level at which predators or parasitoids

depend on primary consumption varies.

Many predator species are facultative con-

sumers of plant-derived food. This category

includes predatory mites (Bakker and Klein,

1992), spiders (Ruhren and Handel, 1999),

*Present address: Netherlands Institute of Ecology, PO Box 40, 6666 ZG Heteren, The Netherlands.

© CAB International 2003. Quality Control and Production of Biological Control Agents:
Theory and Testing Procedures (ed. J.C. van Lenteren) 59

Abstract

It is generally accepted that most parasitoids and many predators require sugar sources, such as nectar or
honeydew, to cover their energetic needs. Protocols for the mass rearing and release of these natural enemies
often take these sugar requirements into account. Nevertheless, the choice of food sources and the methods
of application are usually based on trial and error, due to the fact that basic information on food ecology of
beneficial insects is scarce. In this chapter, an overview is presented of the field of parasitoid food ecology.
After discussing the various ways in which parasitoid fitness can benefit from sugar feeding, various natural
sugar sources are compared in respect of their function in nature and their suitability as parasitoid nutrition.
Given the fact that the choice of the optimal food supplement depends on characteristics of both the food
source and its consumer, either side of the equation is addressed. Sugar sources are compared in respect of
their composition and the volume produced. Parasitoid characteristics addressed include taste perception,
digestive efficiency and food-foraging behaviour. It is argued that the field of food ecology can help in select-
ing food supplements for use in parasitoid rearing as well as application in biological control.