Rapid ʻŌhiʻa Death (ROD) is a fungal disease complex that was first described in 2015. ROD is caused by Ceraotocystis lukuohia and Ceratocystis huliohia, and has killed over one million ʻōhiʻa trees (Metrosideros polymorpha), the keystone native tree species of Hawaiʻi. I will review the science conducted in the last ten years understanding the role of ambrosia beetles in the spread of ROD and how to manage them. When ROD was first discovered it was unknown if insects were invovled in the spread. Beetles were hypothesized to play a role, as they are important vectors in related systems. Years of work determined the ROD pathogens are spread by four invasive ambrosia beetles including Xyleborinus saxesenii, Xyleborus affinis, Xyleborus bispinatus, and Xyleborus perforans through direct vectoring and also through contaminated frass. These beetles are elevation limited on the landscape scale, occupy different niches of ʻōhiʻa trees, and produce variable amounts of frass. We determined the use of semiochemicals to manage beetle populations, including beetle attractants and repellents. We also identified the volatile organic compunds produced in the ROD pathosystem and the associated beetle behavior. Most recently we are exploring ambrosia-Ceratocystis interactions, including Ceraocystis and ambrosia detection in beetle mycangia, gut, and body as well as the extent to which these beetles can survive in Ceratocystis-inoculated media.
