Field Trials With Blends of Pheromones of Native and Invasive Cerambycid Beetle Species

Calcium storage in Malpighian tubules and the putative use for pupal chamber formation in a wood-feeding insect

Cerambycid beetles form a chamber to spend their pupal stages in various forms according to the species. The red-necked longhorn beetle Aromia bungii (Coleoptera: Cerambycidae), which is an invasive pest that severely damages Rosaceae trees, makes a pupal chamber at the end of a tunnel deep in the xylem. Beetle larvae and the closely related species form a calcareous lid at the entrance of a pupal chamber. Previous studies on the closely related species conducted more than century ago suggested that Malpighian tubules (MTs) play a vital role in calcium carbonate accumulation. However, the association between this Ca²⁺ accumulation and pupal chamber lid formation utilizing the possible calcium compounds stored in MTs have not yet been demonstrated. First, we artificially reared A. bungii larvae from eggs in host branches for 100 days and identified the larval developmental status and pupal chamber formation, using X-ray computed tomography. Second, we collected larvae from the branches and observed the internal organs by direct dissection under a microscope. Finally, we analyzed the elemental distribution, particularly calcium, in the larval gut with MTs, using energy dispersive X-ray fluorescence. The results suggest that immature larvae of A. bungii could accumulate Ca²⁺ in the MTs through wood tunneling and feeding activities. Ca²⁺ was stored at the proximal regions in two of the six MTs located posteriorly in the body. Additionally, larvae that formed a calcareous lid at the entrance of pupal chambers in the branches did not store Ca²⁺ in the MTs, suggesting that the larvae of A. bungii used the stored Ca²⁺ in their MTs for lid formation.

Characteristics of Trees Infested by the Invasive Primary Wood-Borer Aromia bungii (Coleoptera: Cerambycidae)

Simple Summary

The red-necked longhorn beetle Aromia bungii is an invasive species that causes damage to Rosaceae trees. In introduced countries, tree damage by A. bungii in many regions, such as orchards, forests, and ornamentals, is a serious problem. Information about the characteristics of pest-infested host trees is helpful for efficiently finding and controlling this beetle. In this study, we investigated the characteristics of infested and uninfested ornamental cherry trees in the field, and speculated as to the traits that are important to infestation. As a result, host trees with rough surface bark, large in size, and weakened conditions are prone to damage by A. bungii. These findings aid in the selection of trees or locations to be surveyed for intrusion detection surveillance, where a high probability of damage can be found, among many candidates in intruded areas. Moreover, this knowledge is useful for prioritizing preventive measures for host trees that are more likely to be attacked in already invaded areas.

Abstract

The expanding distribution and tree damage of the invasive, primary wood-borer Aromia bungii (Coleoptera: Cerambycidae), which kills trees of the Rosaceae family, is a problem in intruded areas. However, the tree characteristics associated with infestation by A. bungii, which are useful for early detection or prioritizing preventive measures, are not well examined. We investigated the presence or absence of tree damage (response variable) in pre- and post- surveys along with tree characteristics (four explanatory variables; bark roughness, size, species, and vigor) on monitoring trees in uninvaded sites (survey for the first trees to be damaged) and already invaded sites (survey for the next trees to be damaged). We evaluated the variables using generalized linear mixed models for each site (i.e., a first trees model and a next trees model). Three tree characteristics (bark roughness, size, and vigor) were included as explanatory variables in both best models, indicating that trees with rough surface bark, large in size, and weakened conditions were more susceptible to A. bungii infestation. The reasons for the difference between the two models (species was only chosen in the next trees model) will be considered in our future work.