Sugar feeding of parasitoids in an agroecosystem: effects of community composition, habitat and vegetation

Abstract

Abstract. 1. Sugar from nectar or from honeydew can prolong parasitoids' lifespan, enhance their fecundity and foraging ability, and thereby increase their pest suppression efficiency. Sugar sources within crop monocultures are considered to be limiting for parasitoids. Nevertheless, only few studies have measured the sugar feeding of parasitoid assemblages in agricultural areas or in surrounding non-crop habitats.2. We used cold anthrone tests to compare the frequency of sugar feeding in parasitoid communities, inside pomegranate orchards and in adjacent natural areas, over two consecutive years. Overall, 40% of the 1610 sampled individuals belonging to 135 species scored positive for sugar.3. Sugar-feeding frequency was lower within the orchards than in the neighbouring natural areas. The proportion of sugar-fed wasps increased with herbaceous vegetation cover, both within and outside the orchards, suggesting that herbs are a sugar-rich habitat. Parasitoids sampled from trees and from herbs within the orchards had similar frequencies of sugar feeding, despite differences in wasp species composition.4. Our results probably overestimate sugar-feeding frequencies in the field because sugar-fed individuals have higher longevity and hence are more likely to be sampled. We propose a simple model to approximate this over-sampling bias and apply it to Encarsia inaron (Aphelinidae), one of the most abundant parasitoids in the samples.5. We conclude that sugar availability potentially limits parasitoid fitness in this agro-ecosystem. This may be due to the low density of plants in natural areas during the Mediterranean summer, and to herbicide applications within the orchards that further suppress non-crop herbs.

Addition of nectar sources affects a parasitoid community without improving pest suppression

“…2), these effects were not consistent across all leek moth life stages or between years. This could be due in part to the dilution of any beneficial effect of nectar feeding by immigration of nectar-fed parasitoids from buckwheat plots into no-buckwheat plots, although the true dispersal abilities of the leek moth parasitoids are not known (Steppuhn and Wäckers 2004;Lee et al 2006;Kishinevsky et al 2018). Though not performed in this study, an analysis of the gut contents of parasitoids found in the no-buckwheat plots could help determine, in part, the extent of any parasitoid migration.…”

The combined effect of host and food availability on optimized parasitoid life‐history traits based on a three‐dimensional trade‐off surface

“…This is especially true in pro‐ovigenic parasitoids in which females emerge with their full egg supply and do not produce additional eggs during their lifetime (Jervis, Heimpel, Ferns, Harvey, & Kidd, 2001; Rivero & Casas, 1999). Several studies have demonstrated that parasitoids may be limited by sugar availability in the field (Heimpel & Jervis, 2005; Kishinevsky, Cohen, Chiel, Wajnberg, & Keasar, 2018; Segoli & Rosenheim, 2013c). Hence, a shortage of sugar sources is likely to increase the risk of time limitation, thereby selecting for higher allocation to initial energy reserves.…”

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

“…These sugar‐rich excretions are called honeydew, and honeydew production contributes to the regulation of osmotic stress during feeding . Honeydew can supply carbohydrates that stimulate oviposition and increase the survival and fecundity of predators and parasitoids . Honeydew also often serves as both an attractant and arrestant for foraging natural enemies, drawing them to prey and holding them in place once they arrive .…”

“…12 Honeydew can supply carbohydrates that stimulate oviposition and increase the survival and fecundity of predators and parasitoids. 8,13,14 Honeydew also often serves as both an attractant and arrestant for foraging natural enemies, 15,16 drawing them to prey and holding them in place once they arrive. 17,18 Indeed, it has been suggested that honeydew is the most abundant and accessible sugar resource available to natural enemies in agricultural fields.…”