Rapid `?hi`a Death (ROD) is an emerging disease on two islands of Hawai`i that has led to extensive mortality of the keystone forest species Metrosideros polymopha on Hawai`i Island since 2011. Artificial inoculation trials were conducted with isolates of the ROD pathogens, Ceratocystis lukuohia (Cl) and C. huliohia (Ch), on forest trees in 2017. Mature trees naturally-infected with either pathogen were also identified for comparative study. Visual results from whole tree dissections of all study trees and results from numerous isolations of the pathogens revealed two distinct diseases that differ in their rate and pattern of colonization within the host and in crown symptom progression. Inoculation of tree main stems with Cl led to 100% crown wilt in five and partial wilt in three of the nine study trees within one or two months of inoculation in mid-June or late August, respectively. Extensive, vertical xylem staining of stems was observed on all nine trees. In contrast, long elliptical bark cankers underlain by reddish-brown sapwood resulted on stems inoculated with Ch, but no crown symptoms were observed within 54 or 91 days after late May and early August treatments, respectively. No disease symptoms were observed on control trees for Ch or Cl trials. After comparing results of artificially-inoculated and naturally-infected trees, we conclude that ROD is actually two diseases, i.e. a systemic wilt disease caused by Cl and a canker disease caused by Ch.