The influence of aphid-produced honeydew on parasitoid fitness and nutritional state: A comparative study

Abstract

Honeydew is a sugar-rich resource excreted by many hemipteran species and is a key food source for other insect species such as ants and parasitoid wasps. Here, we evaluated the nutritional value of 14 honeydews excreted by 13 aphid species for the generalist aphid parasitoid Lysiphlebus testaceipes to test a series of hypotheses concerning variation in the nutritional value of honeydew. There was a positive correlation between the body sugar content of honeydew-fed parasitoids and their longevity. This information is valuable for biological control researchers because it demonstrates that the nutritional state of honeydew-fed parasitoids in the wild can indicate their fitness, independently of the honeydew source they have fed on. Although the carbohydrate content and longevity of L. testaceipes differed greatly among the different honeydews, we did not find a significant effect of aphid or host plant phylogeny on these traits. This result suggests that honeydew is evolutionarily labile and may be particularly subject to ecological selection pressures. This becomes apparent when considering host aphid suitability: Schizaphis graminum, one of the most suitable and commonly used hosts of L. testaceipes, produced honeydew of the poorest quality for the parasitoid whereas Uroleucon sonchi, one of the few aphids tested that cannot be parasitized by L. testaceipes, excreted the honeydew with the highest nutritional value. These data are consistent with the hypothesis that hemipterans are subject to selection pressure to minimize honeydew quality for the parasitoids that attack them.

Honeydew composition and its effect on life‐history parameters of hyperparasitoids

“…When honeydew is present near their hosts, parasitoids have to invest less time in searching for sugar sources, and they can minimise energy and risks associated with searching for nectar, which may be located further away (Wackers et al ., ). Indeed, longevity of aphid parasitoids is generally supported by honeydew, but not all honeydew types are equal in this respect (Hogervorst et al ., ; Tena et al ., ), probably because some honeydew carbohydrates have a larger impact on longevity than do others (Lenaerts et al ., ). Indeed, many factors contribute to variation in the composition of dietary sugars in honeydew, including host plant species (e.g.…”

A sticky situation: honeydew of the pear psylla disrupts feeding by its predator Orius sauteri

“…The nutritional value of honeydew for natural enemies varies between herbivore species, time after excretion, and host plant species . In some cases, honeydew can be a poor source for natural enemies . In addition, honeydew may indirectly release herbivores from top‐down control by benefiting hyperparasitoids or intraguild predators, substituting for prey in natural enemy diets, and reducing foraging efficiency by dirtying predators' mouthparts .…”

“…13,20 In some cases, honeydew can be a poor source for natural enemies. 21,22 In addition, honeydew may indirectly release herbivores from top-down control by benefiting hyperparasitoids or intraguild predators, substituting for prey in natural enemy diets, and reducing foraging efficiency by dirtying predators' mouthparts. 15,23 While the value of honeydew for parasitoids is relatively well-explored, relatively little is known about honeydew's nutritional benefits to predators other than ants.…”

The effects of host plant species on adult oviposition and larval performance of the aphid predator Aphidoletes aphidimyza

“…The quality and quantity of aphid honeydew can be influenced by interactions between plant traits and aphids (Wäckers et al ., ; Tena et al ., ), so honeydew may also have influenced the oviposition behaviour we observed, including the absence of eggs in many replicates. Adult A. aphidimyza feed on aphid honeydew, which increases their survival and fecundity (Markkula et al ., ).…”