Betraying its presence: identification of the chemical signal released by Tuta absoluta-infested tomato plants that guide generalist predators toward their prey

Abstract

Plants modify their volatile chemical signature under pest infestation, which might directly or indirectly improve their defence against threats. These chemical signals have potential in integrated pest management strategies. Macrolophus pygmaeus (Rambur) [Heteroptera: Miridae] is a generalist predatory insect widely used to control the tomato leaf miner, Tuta absoluta (Meyrick) [Lepidoptera: Gelechiidae]. Based on a previous study demonstrating the ability of this mirid species to discriminate non-infested versus T. absoluta-infested tomato plants, our objective was to identify plant volatile chemicals (herbivore-induced plant volatiles—HIPVs) guiding the behaviour of such a generalist predator towards its prey. First, we used coupled gas chromatography-mass spectrometry-electroantennographic detection analysis to screen for active antenna components from the volatile blend released by T. absoluta-infested tomato plants. Dose responses associated with each isolated HIPV were also performed using an electroantennograph. Subsequently, behavioural assays were conducted in a double-choice olfactometer to analyse and identify the behaviourally active chemicals eliciting olfactory responses. Twenty-one total compounds induced antennal responses and six of the 21 evoked positive attractions in M. pygmaeus: (E)hex-2-enal, 2-carene, α-pinene, β-phellandrene, hexanal, and linalool. A synthetic blend of active HIPVs induced olfactory responses as well as attraction in the bioassays. Our results provided evidence the generalist mirid predator M. pygmaeus uses chemical cues from infested tomato plants to identify plants infested by prey. We discussed how these results can be used to improve existing biological approaches to control the tomato leaf miner, T. absoluta.