Do plant volatiles confuse rather than guide foraging behavior of the aphid hyperparasitoid Dendrocerus aphidum?

Abstract

Many species of parasitoid wasps use plant volatiles to locate their herbivorous hosts. These volatiles are reliable indicators of host presence when their emission in plants is induced by herbivory. Hyperparasitoids may also use information from lower trophic levels to locate their parasitoid hosts but little is known about the role of volatiles from the plant–host complex in the foraging behavior of hyperparasitoids. Here, we studied how Dendrocerus aphidum (Megaspilidae) responds to plant and host volatiles in a series of experiments. This hyperparasitoid uses aphid mummies as its host and hampers biological control of aphids by parasitoids in greenhouse horticulture. We found that D. aphidum females were strongly attracted to volatiles from mummy-infested sweet pepper plants, but only when clean air was offered as an alternative odor source in the Y-tube olfactometer. Hyperparasitoid females did not have a preference for mummy-infested plants when volatiles from aphid-infested or healthy pepper plants were presented as an alternative. These olfactory responses of D. aphidum were mostly independent of prior experience. Volatiles from the host itself were also highly attractive to D. aphidum, but again hyperparasitoid females only had a preference in the absence of plant volatiles. Our findings suggest that plant volatiles may confuse, rather than guide the foraging behavior of D. aphidum. Mummy hyperparasitoids, such as D. aphidum, can use a wide variety of mummies and are thus extreme generalists at the lower trophic levels, which may explain the limited role of (induced) plant volatiles in their host searching behavior.

The Ecology of Hyperparasitoids

“…A comparative study on four species of aphid-associated hyperparasitoids concluded that contact cues of mummies and honeydew were more important than olfactory cues in hyperparasitoid host location (10). In contrast, a laboratory study recently showed that female Dendrocerus aphidum are attracted to volatiles from the plant-host complex, but this attraction was likely due to the presence of mummies and not to (induced) plant volatiles (24). Moreover, when attractive mummy hosts were presented in combination with plants, D. aphidum no longer preferred the smell of mummies, suggesting that plant volatiles may confuse foraging hyperparasitoids.…”

“…Pseudo-hyperparasitoids that oviposit on the (pre)pupal stage of their host may use information from the pupal skin or cocoon. Dendrocerus carpenteri and D. aphidum are attracted to aphid mummies, and Siri (102) showed that long-chain compounds may mediate this response, at least at short-range, while de Boer et al (24) showed that mummies can attract D. aphidum over a longer distance as well, suggesting that volatile compounds may be involved too (but see above). After arrival on a plant, aphid-associated hyperparasitoids may be arrested by the presence of honeydew (9), possibly because it is an important food source for them (25).…”

“…These study systems revealed the various life histories, host exploitation patterns, and foraging strategies of hyperparasitoids. Over the past two decades, new discoveries on aphid-associated hyperparasitoids were made on host location (10,24), the cues exploited during host location (9, 38), and the potential of using this knowledge in decreasing the negative impact of hyperparasitoids in biological control (20,65,112). Moreover, the first detailed studies on host location by caterpillar-associated hyperparasitoids have yielded new insights into the cues that hyperparasitoids may exploit in host searching (21,89,139,140,142).…”

Beheersing van bodemplaaginsecten via bodemgezondheidsmaatregelen : Een overzicht van de beschikbare kennis voor een selectie van akkerbouwgewassen met hun bijbehorende bodemplaaginsecten

“…Eén aspect is dat predatoren en parasitoïden ook elkaar bestrijden. Hyperparasitoïden zijn hiervan een voorbeeld die in de kasteelt voor behoorlijke reductie kunnen zorgen van de parasitoïden van bladluizen (De Boer et al, 2020). Hetzelfde geldt voor grotere soorten loopkevers die kleinere soorten eten en zodoende de natuurlijke vijand van bijvoorbeeld Delia vliegen reduceren (Prasad en Snyder, 2004).…”

Natuurvriendelijke bestrijding van bladluizen : voorkómen van hoge populatiedichtheden en curatief bestrijden

“…De hyperparasitoïde voedt zich op de pop van de primaire parasitoïde en voorkomt zo de populatiegroei van de primaire parasitoïde. Onderzoek naar hyperparasitoïden richt zich op dit moment op de kasteelt van paprika waar ze voor aanzienlijke reductie van de primaire parasitoïde kunnen zorgen (de Boer et al, 2020).…”