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First Detection of Aroid Leaf Rust (Pseudocerradoa paullula) on Monstera (Monstera deliciosa) in Hawaii

Posted on Jul. 1, 2025  /  Nursery, Plant Pests  /  Subscribe 0

Figure 1. Caption: Images of Pseudocerradoa paullula found on Monstera deliciosa at a Kauai nursery.

Figure 2. Caption: Yellow leaf spots and brown lesions upper (left) and lower (right) leaf surfaces caused by P. paullula.

Figure 3. Caption: Image of P. paullula uredospores under the compound microscope, viewed at 400x magnification.

P. paullula is a fungal pathogen known to produce lesions about 1 cm in diameter on the lower leaf surface and small chlorotic spots on the upper side during early stages of infection (Figure 2). The lesions develop an orange to reddish-brown pigment with yellow halos and produce round, orange uredospores that have a powdery texture. Infected tissue can brown over time and may become susceptible to secondary pathogens as lesions expand.

Host Range and Distribution

Aroid leaf rust has previously been reported in the Philippines, Australia (Shaw, 1991), New Caledonia, China (Zheng Xiao Hui, 2001), Japan (Sakamoto et. al., 2023), Malaysia (Lee et. al, 2012, Williams, 1976), Taiwan (Chung et. al, 2009), and Papua New Guinea (Shaw, 1984). It has also been detected in the continental United States, from nurseries in Virginia (Bily et al., 2024), South Carolina (Yang et al., 2023), and Florida (Urbina et al, 2023). This pathogen was also intercepted in 2014 at the port of Los Angeles, California from Malaysia (Urbina et. al, 2023).

This fungal pathogen is host-specific. Currently, the most reported host of P. paullula is M. deliciosa. Other Monstera species, such as M. andansonii, M. subpinnata, and M. standleyana, have also been reported to be susceptible (Shaw, 1991). Other known hosts in the Araceae family include Epipremnum pinnatum (taro vine, dragon-tail plant, centipede tongavine) (Fig. 4), Typhonodorum lindleyanum (water banana), Amorphophallus campanulatus (elephant root yam) (Williams & Liu, 1976), Alocasia sp., and Stenospermation andreanum (Yang et. al, 2023, Urbina et. al, 2024).

Figure 4: Images of P. paullula leaf spots on Epiremnum pinnatum (taro vine, dragon-tail plant, centipede tongavine) upper (C) and lower (D) surface (white arrows). Enlarged necrotized leaf spot caused by secondary pathogens (black arrows). Images taken by Romina Gazis, University of Florida: Tropical Research and Education Center.

How does the rust pathogen spread?

This rust pathogen is considered an obligate parasite, meaning it requires living host tissue to complete its life cycle and obtain nutrients (Kolmer et. al, 2009). P. paullula can easily spread with warm temperatures and high humidity conditions, particularly in areas with prolonged periods of rain or dampness. It is known to survive cold temperatures by producing thick-walled teliospores for overwintering (Shaw, 1993). However, Hawaii’s warm climate may not support teliospore formation.

Spores can be spread by wind and splashing water. Plants weakened by disease or insect damage are particularly vulnerable, as these wounds provide entry points for rust spores. The pathogen can also spread by humans through plant trade, and extra precautions should be taken when receiving host plants from locations known to have the rust disease. If you think you have encountered this rust, you can report to 643pest.org or call 643-PEST (643-7378). Tools, equipment, and clothing contaminated with spores can also transmit the pathogen, if not properly disinfected.

Management Practices

There are several effective practices to help prevent the introduction and spread of aroid leaf rust. The important step is to avoid introducing the disease into your landscape. When purchasing known host plants, carefully inspect leaf surfaces for any signs or symptoms of infection. Newly purchased host plants from the countries and states listed above should be isolated and carefully monitored for 40 days to watch for rust development.

To reduce the risk of infection, create an environment that is less favorable to rust. This include minimizing leaf wetness by switching overhead irrigation to drip systems and reducing the frequency of watering. Utilizing thorough sanitization practices by regularly pruning and removing symptomatic leaf tissue, reducing plant debris, washing footwear regularly, and disinfecting tools with a 70% alcohol solution or 10% bleach solution are also helpful practices to minimize infections. The use of registered fungicides for ornamentals may help control P. paullula (Table 1).

How to Discard Plants Affected with Aroid Leaf Rust

When discarding the diseased plant tissue, do not discard the symptomatic leaves in the green waste bin, as this may spread viable spores. Instead, consider composting or burying the infected plant material. If the plant tissue is properly covered and allowed to decompose, the pathogen will die along with the host.

Acknowledgement

Special thanks to William Miller (U.H. Manoa Undergraduate Research Assistant) and Dr. Brent Sipes (U.H. Manoa Nematologist) for their assistance in the Kauai survey trip. We would also like to thank Dr. Marian Luis (U.H. Manoa Mycologist) and her lab for their assistance in molecular identification.

Table 1. Fungicides registered in Hawaii and labeled for rust pathogens on Monstera and other ornamental plants.

These are some pesticides which are labeled for use on residential ornamentals, don't have restrictive personal protective equipment (PPE) requirements, and have been shown to be effective at controlling fungal pathogens. There may be products not listed here which would also be effective against rust. Whenever you use a pesticide, make sure that the site of application is listed on the label, that you wear all required PPE, and that you follow any relevant label restrictions like maximum annual use rates and environmental protections.

References:

Bily D, Gyatso T, Evans A. 2024. First Detection of Pseudocerradoa paullula Causing Aroid Leaf Rust on Swiss Cheese Plant (Monstera deliciosa) in Virginia. Plant Disease 108(11), 3412.

Chua, L.S.L., Lee, S.S., Alias, S.A., Jones, E.G.B., Zainuddin, N. & Chan, H.T. 2012. Checklist of Fungi of Malaysia, Issue/No. 132. Forest Research Institute Malaysia (FRIM), Malaysia. 556.

Chung, W. H., Ono, Y., Kakishima, M., & Haung, J. W. 2009. The New Geographical Distribution of Rust Fungi from Taiwan. Taiwania, 54(3), 279-282.

Kolmer, J. A., Ordonez, M. E., & Groth, J. V. (2009). The rust fungi. Encyclopedia of life sciences (ELS), 10(9780470015902), a0021264.

Neal, M. C. 1965. In Gardens of Hawai'i. Revised Edition. Bernice P. Bishop Museum Special Publication 40. Bishop Museum Press, Honolulu, HI

Rauch, F. 1997. Monstera.

Sakamoto A., Uzuhashi S., Hoshi H., Kubota M., Horie H., and Kakishima M. 2023. First Report of Rust Caused by Puccinia paullula on Monstera deliciosa and M. adansonii in Japan. Plant Disease 107(2), 570.

Shaw, D.E. 1984. Microorganisms in Papua New Guinea. Dept. Primary Ind., Res. Bull. 33, 1-344.

Shaw, D. E. 1991. Rust of Monstera deliciosa in Australia. Mycological Research, 95(6), 665-678.

Shaw, D.E., 1993. A note on the further occurrence and viability of teliospores of Puccinia paullula f. sp. monsterae. Australasian Plant Pathology, 22(1), 19-21.

Urbina, H., Jones, C., Moore, M.R. and Gazis, R., 2024. Susceptibility of Centipede Tongavine, Epipremnum pinnatum, Commercially Grown in Nurseries in Florida to Aroid Leaf Rust, Pseudocerradoa paullula. Plant Disease, 108(1), 217.

Urbina, H., Jones, C., Moore, M.R. and Gazis, R., 2023. Detection of Aroid Leaf Rust Pseudocerradoa paullula on Swiss Cheese Plant Monstera deliciosa in the Continental United States. Plant Disease, 107(8), 2520.

Williams, T.H., and Liu, P.S.W. 1976. A host list of plant diseases in Sabah, Malaysia. Commonwealth Mycological Institute Phytopathological Papers 19: 1-67.

Yang, X., Colburn, G. C., Roach, K., Zee, T., & Long, S. H. 2023. First Report of Pseudocerradoa paullula Causing Aroid Leaf Rust on Swiss Cheese Plant (Monstera deliciosa) in South Carolina, USA. Plant Disease, 107(9), 2871.

Zheng XiaoHui, Z. X., Qi PeiKun, Q. P., & Jiang ZiDe, J. Z. 2001. Identification on the fungal diseases of ornamental plant (Araceae) in Guangzhou region-II. Journal of South China Agricultural University 22(1): 51-53.0

Sydney Ward, Maxwell Bendes, and Josiah Marquez, PhD Plant Pathologist,

[email protected], Plant Pathology Unit, Department of Agriculture, State of Hawaii, 99-941 Halawa Valley Street, Aiea, HI 96701

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