The Influencing Factors of Aggregation Behavior of Tree-of-Heaven Trunk Weevil, Eucryptorrhynchus brandti (Harold) (Coleoptera: Curculionidae)

Simple Summary The tree-of-heaven trunk weevil Eucryptorrhynchus brandti is a significant pest of the tree of heaven Ailanthus altissima, often leading to Ailanthus altissima death. Eucryptorrhynchus brandti adults usually aggregate to overwinter in soil or areas dense with weeds, and congregate on the bare phloem of the tree of heaven in the field during the non-winter months regardless of whether the trees are healthy or injured. Aggregation is a common phenomenon, and conspecific individuals gather in a limited area of the environment and increase social interaction. In this study, some factors were tested in the laboratory, indicating the environmental factors, potential chemical cues, and some physical signals that had the most significant effects on the aggregation behavior of E. brandti adults. This study of the aggregation behavior of E. brandti adults contributes to understanding communications and interactions among conspecific individuals. The tree-of-heaven trunk weevil, Eucryptorrhynchus brandti (Harold) (Coleoptera: Curculionidae), is one of the most harmful pests that damage the tree of heaven, Ailanthus altissima Swingle (Sapindales: Simaroubaceae). Aggregation behavior tests of E. brandti adults were conducted in laboratory conditions. The effects of temperature and light on the aggregation behavior of adults were tested, and the effect of sex and host was conducted with binomial choice experiments. The results showed that (1) the adults aggregate in both light and dark environments but preferred the dark environment, (2) temperature can drive the aggregation of E. brandti adults, (3) host plants could trigger E. brandti adults' aggregation behavior, which is probably related to phytochemicals and insect feeding and localization, (4) there was mutual attraction of males and females and chemical attraction of crude intestinal extracts of males and females, and (5) aggregation behavior of E. brandti adults may also be related to the mediating of physical signals in insects. In this study, aggregation behavior can help us understand conspecific interactions and discover some strategies for effective control.