Pillar coral (Dendrogyra cylindrus) is a rare Caribbean coral with only one species in its genus. Because of population declines, the species was listed as threatened under the U.S. Endangered Species Act in 2014 (Federal Register 2014). By 2020, the species had further catastrophic population declines of an estimated 70 % along the Florida Reef Tract from back-to-back bleaching events, white plague, and a spreading disease now referred to as stony coral tissue loss disease (SCTLD) (Precht 2016; Neely et al. 2017; FKNMS 2018). The estimated number of surviving genotypes within the Florida population has declined from 181 to 51 (Neely personal communication March 2020). The remaining population is assumed to be reproductively extinct and at high risk for regional extinction (Neely et al. 2017). At least 40 of the remaining genotypes are heavily diseased or have less than 5% tissue remaining (Neely et al. 2020). In 2016, a multi-institutional collaboration was initiated to rescue remaining genotypes from the wild and place them into ex situ and in situ nurseries. As part of this effort, the NOAA NOS NCCOS Coral Health and Disease Program participated by conducting exploratory experimentation to treat, recover and rehabilitate diseased D. cylindrus genotypes.