Honeydew Is a Food Source and a Contact Kairomone for Aphelinus mali
1
Instituto de Investigación y Tecnología Agroalimentaria (IRTA)-Campus de la Escola Tècnica Superior d’Enginyeria Agrària (ETSEA), Protecció Vegetal Sostenible, Av. Rovira Roure 191, 25198 Lleida, Spain
2
IRHS, INRAE, Institut Agro, Université d’Angers, 49071 Beaucouzé, France
3
IGEPP, INRAE, Institut Agro, Université de Rennes, 49000 Angers, France
4
Laboratorio de Control Biológico, Instituto de Ciencias Biológicas, Universidad de Talca, Talca 3465548, Chile
*
Author to whom correspondence should be addressed.
Insects 2023, 14(5), 426; https://doi.org/10.3390/insects14050426
Submission received: 15 March 2023
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Revised: 18 April 2023
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Accepted: 24 April 2023
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Published: 29 April 2023
(This article belongs to the Special Issue Trophic Resources for Parasitoids in Agroecosystems)
Simple Summary
Natural enemies of major pests such as parasitoids require sugar-rich food for development and reproduction. In agricultural fields, honeydew excreted by aphids is often the predominant sugar source that parasitoids can consume. Moreover, honeydew can constitute a cue used by parasitoid females to find their aphid host. However, in some species, such as the woolly apple aphid (Eriosoma lanigerum), honeydew is coated with a thin layer of wax, which could make its consumption harder and prevent the emission of attractive odors for parasitoids. In the present study, we evaluated the benefits in terms of longevity and host searching that could provide honeydew to the main parasitoid of the woolly apple aphid, Aphelinus mali, and infer parasitoid feeding patterns in apple orchards. Results suggested that A. mali is able to consume honeydew in laboratory and field conditions and to benefit from honeydew, as it increased its longevity when honeydew was provided with water. Although no olfactory preference was observed, honeydew also stimulated oviposition by A. mali. The contribution of honeydew to increase the efficiency of A. mali as a biological control agent is discussed.
Abstract
Many parasitoids need to feed on sugar sources at the adult stage. Although nectar has been proven to be a source of higher nutritional quality compared to honeydew excreted by phloem feeders, the latter can provide the necessary carbohydrates for parasitoids and increase their longevity, fecundity and host searching time. Honeydew is not only a trophic resource for parasitoids, but it can also constitute an olfactory stimulus involved in host searching. In this study, we combined longevity measurements in the laboratory, olfactometry and feeding history inference of individuals caught in the field to test the hypothesis that honeydew excreted by the aphid Eriosoma lanigerum could serve as a trophic resource for its parasitoid Aphelinus mali as well as a kairomone used by the parasitoid to discover its hosts. Results indicate that honeydew increased longevity of A. mali females if water was provided. Water could be necessary to feed on this food source because of its viscosity and its coating by wax. The presence of honeydew allowed longer stinging events by A. mali on E. lanigerum. However, no preference towards honeydew was observed, when given the choice. The role of honeydew excreted by E. lanigerum on A. mali feeding and searching behavior to increase its efficiency as a biological control agent is discussed.
Keywords:
parasitoids; sugars; biological control; Eriosoma lanigerum; chemical cues
