Hibiscus on Oʻahu being infected by mysterious viruses, UH researchers discover

Hibiscus plants in Hawaiʻi are being infected by two new viruses that could pose a threat to the state flower, the yellow hibiscus, according to researchers in the College of Tropical Agriculture and Human Resources at the University of Hawaiʻi at Mānoa.

Their findings were published in Viruses.

“Do these viruses pose a threat to the survival of hibiscus?” asked John Hu, a plant pathologist with the UH Mānoa Department of Plant and Environmental Protection Sciences. “That’s exactly the question we want to answer. Our early findings indicate it could, however we don’t know the final answer yet. We plan to do more virus surveys, including testing the mother plants at the propagation (the breeding of specimens) site.”

The pair of viruses are called hibiscus betacarmovirus and hibiscus soymovirus. Infected hibiscus plants show mosaic, ringspot and chlorotic (yellowing of healthy green leaves due to lack of chlorophyll) spots on their leaves.

They were discovered through analyzing 54 hibiscus samples collected in Honolulu — 34 from 18 locations on the UH Mānoa campus. The remaining 20 were collected from a variety of sites from Diamond Head to downtown.

Twelve of the 54 samples (22%) were positive for at least one of the viruses. One sample tested positive for hibiscus betacarmovirus, nine samples tested positive for hibiscus soymovirus and two samples tested positive for both viruses.

Similar viruses called hibiscus latent Fort Pierce virus and hibiscus latent Hawaiʻi virus have previously been discovered infecting hibiscus plants in Hawaiʻi by the same group of researchers.

The team is led by Hu and Michael Melzer, associate researcher with the UH Mānoa Department of Plant and Environmental Protection Sciences. Hu and Melzer have been conducting research on hibiscus viruses for more than 10 years.

“The main concern is whether these viruses infect and impact our native hibiscus, some of which are threatened and endangered,” Melzer said. “Cleaning tools when pruning hedges will help to prevent the spread of the mechanically-spread viruses.”