Salicinoid phenolics reduce adult Anoplophora glabripennis (Cerambicidae: Lamiinae) feeding and egg production

Plant chemistry plays an important role in mediating resistance against insect herbivores. Depending on insect species and feeding strategies, plant defenses can prevent insect attacks, impact digestive physiology and influence reproductive output. The Asian longhorned beetle (Anoplophora glabripennis) is an invasive, tree-killing insect that exploits multiple host plant species. Anoplophora glabripennis is documented to attack Populus spp., but the ability for adults to consume Populus varies between beetle populations. In this study, we explored the influence of salicinoid phenolic glycosides, known to be potent chemical defenses in Populus against generalist insects, on A. glabripennis adult behavior and fecundity. We performed a series of choice- and no-choice experiments using extracts of salicinoids applied to plants that do not produce these compounds. Salicinoids affected A. glabripennis performance in a dose-dependent manner, with higher concentrations significantly reducing feeding. Egg development was reduced by > 90% in females fed salicinoids at ~ 1.3% dry weight. We then compared salicinoids present in feeding material vs. frass and found both a decrease in concentration and a shift in composition of these compounds. However, some of the more complex salicinoids were unchanged in the excrement, suggesting minimal detoxification had occurred. Our results show that salicinoids disrupt egg development in A. glabripennis, thereby reducing fitness. These results have implications for how A. glabripennis metabolizes plant defense chemicals and how tolerance may vary among populations.