Catering to the nutritional needs of natural enemies: Honeydew vs. nectar

The majority of predators and parasitoids feed on sugar sources to cover their enegetic needs. Sources of sugars exploited by 'carnivorous' arthropods include (extra) floral nectar, and honeydew, the excretions from phloem feeding insects. Sugar feeding can have a dramatic impact on longevity, fecundity, and distribution of predators and parasitoids. Each of these parameters affects herbivore-carnivore dynamics in the field. In absence of suitable sugar sources, the effectiveness of biological pest control can be severely compromized. As modern agricultural systems are often characterized by a scarcity of floral resources, honeydew is often the predominant sugar source available. While the effect of flowers on natural enemies has been well studied, relatively little is known about the role of honeydew as a food source for sugar feeding arthropods. Here we will compare the suitability of nectar and honeydew as food sources for parasitoids/predators and present results from chemical analytical methods to reveal to what extent these sugar sources contribute to the diet of predators and parasitoids under field conditions.