First report of Plasmopara sphagneticolae on the native Hawaiian plant Lipochaeta integrifolia

Authors: DAVIS, WILLIAM - Oak Ridge Institute For Science And Education (ORISE); KO, MANN - Hawaii Department Of Agriculture; OCENAR, JODIE - Hawaii Department Of Agriculture; ROMBERG, MEGAN - Animal And Plant Health Inspection Service (APHIS); Crouch, Jo Anne

Submitted to: Australasian Plant Disease Notes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2020
Publication Date: 7/8/2020
Citation: Davis, W.J., Ko, M., Ocenar, J.R., Romberg, M., Crouch, J. 2020. First report of Plasmopara sphagneticolae on the native Hawaiian plant Lipochaeta integrifolia. Australasian Plant Disease Notes. 15(1):29. https://doi.org/10.1007/s13314-020-00398-5.
DOI: https://doi.org/10.1007/s13314-020-00398-5

Interpretive Summary: Nehe is a flowering native Hawaiian plant used for lei making. Like many plants endemic to the Hawaiian islands, nehe populations are threatened by habitat destruction and are vulnerable to extinction. Diseases have never been reported from nehe or related plants in the genus Lipochaeta. However, disease-damaged nehe plants were recently found on the islands of Oahu and Hawai'i. In a collaborative effort between USDA-ARS, USDA-APHIS, and the Hawai'i Department of Agriculture, this research identified the new nehe disease as a downy mildew, a type of disease caused by water molds. DNA analysis and microscopy identified the water mold as one that has been found just once before, infecting invasive creeping ox-eye weeds in Australia. The identification of this pathogen affecting nehe plants is the first step towards developing control measures that can be specifically targeted against the pathogen. Plant pathologists, extension personnel, and regulatory officials will use this research to identify and prevent the spread of this disease.

Technical Abstract: Downy mildew disease was observed for the first time from Lipochaeta integrifolia, a G3-vulnerable plant native to Hawai'i. The oomycete infecting the plants was identified as Plasmopara sphagneticolae. This marks the first report of P. sphagneticolae outside of Australia on a new host. This disease may have significant implications for conservation efforts of L. integrifolia and other endangered native Asteraceae on the islands.