Chemical cues from honeydew and cuticular extracts of trialeurodes vaporariorum serve as kairomones for the parasitoid Encarsia formosa

Ayelo Pascal Mahukpe, Yusuf Abdullahi A., Chailleux Anaïs, Mohamed Samira A., Pirk Christian W.W., Deletre Emilie. 2022. Chemical cues from honeydew and cuticular extracts of trialeurodes vaporariorum serve as kairomones for the parasitoid Encarsia formosa. Journal of Chemical Ecology, 48 (4) : 370-383.

Résumé : Kairomones are semiochemicals that are emitted by an organism and which mediate interspecific interaction that is of benefit to an organism of another species that receives these chemical substances. Parasitoids find and recognize their hosts through eavesdropping on the kairomones emitted from the by-products or the body of the host. Hemipteran insect pests feed on plant sap and excrete the digested plant materials as honeydew. Honeydew serves as a nutritional food source for parasitoids and a medium for micro-organisms whose activity induces the release of volatiles exploited by parasitoids for host location. The parasitoid Encarsia formosa preferentially parasitizes its host, the greenhouse whitefly, Trialeurodes vaporariorum, on tomato Solanum lycopersicum, but little is known about the chemicals that mediate these interactions. We investigated the olfactory responses of the parasitoid E. formosa to odours from honeydew and nymphs of T. vaporariorum in a Y-tube olfactometer. Arrestment behaviour of the parasitoid to honeydew and nymph extracts, as well as to synthetic hydrocarbons, was also observed in Petri-dish bioassays. We found that T. vaporariorum honeydew volatiles attracted the parasitoid E. formosa but odours from the whitefly nymphs did not. We also found that the parasitoid spent more time searching on areas treated with extracts of honeydew and nymphs than on untreated areas. Gas-chromatography-mass spectrometric analysis revealed that the honeydew volatiles contained compounds such as (Z)-3-hexenol, δ-3-carene, 3-octanone, α-phellandrene, methyl salicylate, β-ocimene, β-myrcene, and (E)-β-caryophyllene which are known to be attractive to E. formosa. The cuticular extracts of the nymphs predominantly contained alkanes, alkenes, and esters. Among the alkanes, synthetic nonacosane arrested the parasitoid. Our findings are discussed in relation to how the parasitoid E. formosa uses these chemicals to locate its host, T. vaporariorum.

Mots-clés Agrovoc : kairomones, parasitoïde, Solanum lycopersicum, Encarsia formosa, Trialeurodes vaporariorum, miellat, ravageur des plantes, encarsia, substance sémiochimique, Trialeurodes, substance chimique, sous-produit

Mots-clés libres : Parasitoid foraging, Cuticular hydrocarbons, Nonacosane, Host-parasitoid interactions, Olfactometer, Biological Control

Classification Agris : H10 - Ravageurs des plantes
F60 - Physiologie et biochimie végétale

Champ stratégique Cirad : CTS 4 (2019-) - Santé des plantes, des animaux et des écosystèmes

Agences de financement hors UE : Agence Nationale de la Recherche

Projets sur financement : (FRA) Utilisation de composés sémiochimiques combinée à de la protection physique pour concevoir un système de production écologiquement intensif.

Auteurs et affiliations

• Ayelo Pascal Mahukpe, ICIPE (KEN) - auteur correspondant
• Yusuf Abdullahi A., University of Pretoria (ZAF)
• Chailleux Anaïs, CIRAD-PERSYST-UPR HortSys (SEN)
• Mohamed Samira A., ICIPE (KEN)
• Pirk Christian W.W., University of Pretoria (ZAF)
• Deletre Emilie, CIRAD-PERSYST-UPR HortSys (KEN)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/606398/)

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