Contrasting Behavioral and Electrophysiological Responses of Eucryptorrhynchus scrobiculatus and E. brandti (Coleoptera: Curculionidae) to Volatiles Emitted from the Tree of Heaven, Ailanthus altissima

Simple SummaryEucryptorrhynchus scrobiculatus(Motschulsky) andE. brandti(Harold) are significant pests of tree of heaven,Ailanthus altissima, often leading to tree death. Monitoring systems that involve host–plant based attractants need to be developed for both insect pest species. Here, we compared the behavioral and electrophysiological responses ofE. scrobiculatusandE. brandtito volatiles emitted by various parts of the host plant. Host plant-derived volatiles showed to play a greater role in the foraging behavior ofE. brandtithan inE. scrobiculatus. Volatile components of phloem were found to be particularly attractive toE. brandti.AbstractEucryptorrhynchus scrobiculatusandE. brandti(Coleoptera: Curculionidae) are host-specific pests ofAilanthus altissima(Mill.) Swingle (Sapindales: Simaroubaceae), causing extensive damage to the host. There are no effective attractants available for pest management. The main aim of this study was to explore the role of host plant-derived volatiles in the behavioral response of both weevil species. In a field experiment, both weevil species showed positive response to phloem, and there was no preference for phloem associated with healthy or injured trees. Significantly moreE. brandtiadults responded to the olfactory treatments compared toE. scrobiculatus. In a large-arena experiment, both males and females ofE. scrobiculatussignificantly preferred phloem from the tree trunk while adults ofE. brandtiresponded in significantly greater numbers to tree limbs than to any other parts of host. Females and males ofE. scrobiculatusresponded positively to all parts of host tested in the Y-tube bioassay, whileE. brandtiadults were only attracted by the phloem from healthy and injured trees. There were dissimilar electroantennographic responses to compounds such as 1-hexanol and (1S)-(−)-β-pinene between the two weevil species. This study represents the first report documenting behavioral and electrophysiological responses ofE. scrobiculatusandE. brandtito volatiles from various parts ofA. altissimaand findings may aid efforts to develop attractants.Keywords:host plant volatiles;semiochemical;feeding selection;behavior;physiology