Caterpillar-Induced Plant Volatiles Attract Adult Tortricidae

Feeding Volatiles of Larval Sparganothis pilleriana (Lepidoptera: Tortricidae) Attract Heterospecific Adults of the European Grapevine Moth

Plants release volatiles in response to caterpillar feeding. These herbivore-induced plant volatiles (HIPVs) attract natural enemies of the herbivores and repel or attract conspecific adult herbivores in a tri-trophic interaction which has been considered to be an indirect plant defense against herbivores. Recently, we demonstrated the attraction of male and female European grapevine moth, Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae) to a blend of phenylacetonitrile and acetic acid, two compounds identified as HIPVs in heterospecific apple-leafroller interactions. The ecological basis of our findings is not clearly understood. Thus, this work was undertaken to investigate HIPVs in the grapevine-leafroller interaction and study the response of heterospecific adults L. botrana, to these volatiles. We collected headspace volatiles emitted from uninfested grapevines and grapevines infested with larvae of a generalist herbivore, the grapevine leafroller moth, Sparganothis pilleriana (Denis & Schiffermüller), and analyzed them using gas chromatography/mass spectrometry. Infested grape leaves released three compounds (phenylacetonitrile, indole, and 2-phenylethanol) not found from uninfested leaves. Nine different blends, comprising a full factorial set of the three compounds with each blend containing acetic acid, were tested in a field-cage trial. Only lures containing phenylacetonitrile caused a significant increase in trap catches compared to the other lures and blank traps. Electroantennographic tests show that L. botrana can detect the compounds. The results confirm our hypothesis that phenylacetonitrile is released during grapevines infestation with herbivores, and attracts adult L. botrana.

Leafroller-induced phenylacetonitrile and acetic acid attract adult Lobesia botrana in European vineyards

We recently identified unique caterpillar-induced plant volatile compounds emitted from apple leaves infested with the larvae of various leafroller species. In subsequent field tests, binary blends of phenylacetonitrile+acetic acid and 2-phenylethanol+acetic acid were found to be attractive to a range of tortricid leafroller species (Tortricidae: Tortricinae) in both the Southern and Northern Hemispheres. In this work, the caterpillar-induced plant volatiles from the apple-leafroller system were tested in two vineyards in Spain and Hungary for their attractiveness to the grape frugivore Lobesia botrana (Tortricidae: Olethreutinae). As seen for Tortricinae species, a binary blend of phenylacetonitrile+acetic acid attracted significantly more male and female L. botrana to traps than acetic acid or blank lures. Traps baited with other caterpillar-induced plant volatile compounds (benzyl alcohol, 2-phenylethanol, indole, and (E)-nerolidol, each as a binary blend with acetic acid) did not catch significantly more moths than traps containing acetic acid alone. The catches of male and female moths support an optimistic future for new products in female tortricid surveillance and control that are based on combinations of kairomone compounds released from larval-damaged foliage.