Abstract
The pine weevil, Hylobius abietis, is a severe forest pest insect as it feeds on newly planted conifer seedlings. To identify and develop an antifeedant could be one step towards the protection of seedlings from feeding damage by the pine weevil. With the aim to trace the origin of the antifeedants previously found in feces of the pine weevil, we investigated the culturable bacteria associated with the gut and identified the volatiles they produced. Bacterial isolates were identified by 16S ribosomal RNA gene analysis. The volatile emissions of selected bacteria, cultivated on NB media or on the grated phloem of Scots pine twigs dispersed in water, were collected and analyzed by solid-phase microextraction gas chromatography-mass spectrometry. The bacterial isolates released a variety of compounds, among others 2-methoxyphenol, 2-phenylethanol, 3-methyl-1-butanol, 1-octen-3-ol, 3-octanone, dimethyl disulfide, and dimethyl trisulfide. A strong antifeedant effect was observed by 2-phenylethanol, which could thus be a good candidate for use to protect planted conifer seedlings against feeding damage caused by H. abietis.
Highlights
The pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae), is regarded as a severe pest of conifer reforestations in large parts of Europe and Asia [1]
Bacteria isolated from pine weevil guts were identified based on 16S ribosomal RNA gene sequencing analysis
After an initial screening of all isolates for headspace volatiles, three isolates were chosen for further analysis based on both their large differences in volatile profiles when growing in nutrient broth (NB) medium and their emission of potential antifeedant aromatic compounds
Summary
The pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae), is regarded as a severe pest of conifer reforestations in large parts of Europe and Asia [1]. The adult weevils feed on tender bark containing large amounts of terpenes and phenolics [2,3,4] of a wide range of conifer trees [5], with Scots pine (Pinus sylvestris (L.)) and Norway spruce (Picea abies (L.) H. Feeding weevils are especially destructive for newly planted conifer seedlings, which they frequently kill by girdling the stem [8]. Female weevils lay their eggs either in the soil near roots or in specific egg cavities gnawed into the root bark [9]. The egg is deposited together with feces in the cavity, and the cavity is sealed with a plug made of frass (fragments nibbled from the outer bark) [10]
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