Unknown Distribution and Threat of Sea Grape Rust (Uredo uviferae) in Hawaii
Posted on Jan. 29, 2025 / Plant Pests / Subscribe 0
By: Kimi Kawasaki and Josiah Marquez
Introduction
The Sea Grape tree (Coccoloba uvifera; Fig. 1) is a popular ornamental along Hawaii’s shoreline as a coastal windbreak hedge (Little and Skolmen, 1989) because of its ability to withstand salt, drought, and windy conditions, stabilizing coastal soils (Gilman and Watson, 1993, Ono, 2020). As the common name implies, these trees produce drooping grapelike fruit clusters that ripen to a purple color (Fig. 2 and 3). These edible fruits are made into jelly and wine in tropical America (Little and Skolmen, 1989). They are known to be hardy plants with few diseases and pests. However, there is a pathogen that infects Sea Grape, Uredo uviferae, also known as the sea grape rust.
Figure 1. Sea grape tree growing along the shoreline. Photo Credit: https://delraybeachhistory.org/blog/our-native-sea-grape/.
Figure 2. Unripe sea grape fruit clusters. Photo Credit: Drew Danielson, https://commons.wikimedia.org/wiki/File:Seagrape_(Coccoloba_uvifera)_fruit_at_Playa_Lucia,_Yabucoa,_Puerto_Rico.jpg.
Figure 3. Ripening sea grape fruit clusters. Photo Credit: Daniel di Palma, https://commons.wikimedia.org/wiki/File:Seagrape-bunch02.JPG.
Detection, Distribution & Monitoring
The native range of Sea Grape rust is along the coasts of southern Florida, the Caribbean, and tropical Americas (Parrotta, 1994). In Hawaii, sea grape rust was first reported in 2005 in Papuikou on the eastern coast of the island of Hawaii by a Japanese researcher, Dr. Yoshitaka Ono, at the Ibaraki University and recently detected on Oahu by a Hawaii Department of Agriculture (HDOA) plant inspector during an inter-island nursery inspection. The suspected disease was tentatively diagnosed with an infection of Uredo uviferae (Fig. 4 and 5) by the HDOA Plant Pathology Unit (HDOA-PPU) and confirmed by the USDA Animal and Plant Health Inspection Service Plant Pathogen Confirmatory Diagnostics Laboratory in Laurel, MD. The statewide distribution of this pathogen is not known and could be established on every island. If you suspect this rust in Kauai, Maui, Molokai, or Lanai, please contact HDOA-PPU ([email protected]) or your local University of Hawaii extension agent (https://cms.ctahr.hawaii.edu/ce/Find-Us).
Figure 4. Rust pustules (Uredinia) on the lower leaf surface producing orange urediniospores. Photo Credit: Josiah Marquez.
Figure 5. Urediniospores from rust pustules on the lower leaf surface of Sea Grape leaf at 400x magnification. Photo Credit: Josiah Marquez.
Background and Significance
Sea grape rust was first reported in Florida in 1960 (USDA, 1960). Subsequent reports were made in Puerto Rico and Venezuela in 1962 and 1973, respectively (Roure, 1962; Dennis, 1973). The impacts of sea grape rust are currently unknown, however, this pathogen could cause unsightly leaf spots and defoliation, resulting in Sea Grape decline. In areas with high humidity and rainfall, trees may be at a higher risk of developing more severe symptoms (Nelson, 2012).
Signs, Symptoms, and Management
The main symptoms of Sea Grape rust are reddish-purple spots or lesions on the leaf underside that are distributed in a scattered or densely grouped pattern (Fig 6). The lesions erupt to reveal a powdery mass of reddish-orange spores which are then carried by the wind and spread to other trees (Ono, 2020). To limit the spread of sea grape rust, we suggest implementing general rust disease management tactics like avoiding transplanting rust-infected seedlings or plant material into rust-free areas, removing severely infested leaves, disposing of fallen leaves, sanitizing tools in between plants, intercropping with other tree species, and improving aeration of the tree canopy (Nelson, 2012).
Figure 6. Red leaf spot symptoms on the upper (A) and lower (B) leaf surface. Photo Credit: Josiah Marquez.
References
Dennis, R.W.G. 1973. Fungus Flora of Venezuela and Adjacent Countries. Mycologia. 65:493-494.
Gilman, E.F. and Watson, D.G. 1993. Coccoloba uvifera seagrape. US Forest Service. Fact Sheet ST-175. https://hort.ifas.ufl.edu/database/documents/pdf/tree_fact_sheets/cocuvia.pdf
Little, E.L. and Skolmen R.G., 1989. Common Forest Trees of Hawaii: Native and Introduced (Vol. 679). US Department of Agriculture, Forest Service.
Nelson, S. 2012. Rust of tree heliotrope. College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. Extension Article PD-88. https://www.ctahr.hawaii.edu/oc/freepubs/pdf/PD-88.pdf
Ono, Y. 2020. Additional records of rust fungi (Pucciniales) in the Hawaiian Islands. College of Education, Ibaraki University. https://www.researchgate.net/publication/340011374_Additional_records_of_rust_fungi_Pucciniales_in_the_Hawaiian_Islands
Parrotta, J.A. 1994. Coccoloba uvifera (L.) L. Sea grape, Uva de playa. US Forest Services. https://data.fs.usda.gov/research/pubs/iitf/sm_iitf074%20%20(5).pdf
Roure, L.A. 1962. The Rusts of Puerto Rico. ProQuest Dissertations & Theses.
USDA. 1960. Index of Plant Diseases in the United States. Agricultural Handbook No.165. https://archive.org/details/IndexOfPlantDiseasesInTheUS/mode/1up
Kimi Kawasaki,
[email protected], Plant Pathology Unit, Department of Agriculture,
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