Invader from the dark side

Invader from the dark side

Hot Topics in Ecology

Invader from the dark side

Synthesis by DYP Tng, MW Goosem, CP Paz, and SGW Laurance, James Cook University
Thicket-forming, shade-tolerant Psidium cattleianum spells ecological disaster for World Heritage Area rainforests. Inset: fruits (top) and dense multi-stems (bottom)

Environmental weeds typically invade open, disturbed areas or vegetation edges, and can have devastating ecological and economic consequences. The National Weeds List in Australia informs the public and land managers on weeds prioritized for management, but shade-tolerant weeds that can invade forest ecosystems are inadequately listed. Such weeds are now globally recognized for their ability to impact native vegetation. The Cherry Guava (Psidium cattleianum) from Brazil, a shrub of the Myrtle family (Myrtaceae), is an exceptional example.

1. Cherry Guava was probably introduced to Australia for its edible fruits. The earliest record (1940s) was in Koah, Far North Queensland. Currently, Cherry Guava infestations are found in three World Heritage Areas in Australia: the Wet Tropics in Queensland; Gondwanan Rainforests of Queensland/New South Wales, and Lord Howe Island. It is listed as a noxious weed only in NSW. There are no Australian regulations restricting import or sale.

2. The Global Invasive Species Database lists Cherry Guava among the World’s 100 Worst Weeds – it tolerates shade; grows and matures rapidly; produces a heavy fruit set and seedling bank; is spread by native and feral animals; coppices extensively; and forms multi-stemmed thickets. It can displace native vegetation. Infestations in Australia appear free of natural enemies and resistant to Myrtle Rust which affects co-occurring native members of the Myrtaceae. In Hawaii, Seychelles and Mascarene Islands, natural forested ecosystems are severely impacted after introductions in the early- to mid-1800s.

3. Cherry Guava spread is ongoing, but given the recent Australian history and localized infestations, eradication may be possible with incisive intervention. Government listings and restricting import and sale are first steps. Options to eliminate infestations could combine ecotourism, volunteers and biological control agents.

Hot Topic Lead Author: 
Name: David YP Tng
Phone: 07 4042 1467

Name: MW Goosem

Name: CP Paz

Name: SGW Laurance

ID Title Location Type
7641 Atlas of Living Australia.2014. URL: (Accessed: 11 Dec 2014). Australia User defined search for taxon records and distribution.
7642 Auld T.D., & Hutton I. (2004). Conservation issues for the vascular flora of Lord Howe Island. Cunninghamia 8, 490-500. Lord Howe Island, Australia Descriptive review paper
7643 Cooper W, Cooper WT. (2004) Fruits of the Australian Tropical Rainforest. Nokomis Editions, Victoria, Australia. Tropical Australia Observational study
7644 Fleischmann K. (1997) Invasion of alien woody plants on the islands of Mahé and Silhouette, Seychelles. J. Veg. Sci. 8, 5-12. Mahé and Silhouette islands of the Seychelles chain of islands Measurative experiment using field surveys.
7645 Global Invasive Species Database. 2014. Psidium cattleianum. [Accessed 9th December 2014] Global Descriptive Natural experiment comparing plant functional traits of representative tree species across rain forest - open forest boundaries.
7646 Huenneke L. F., Vitousek P. M. (1990) Seedling and clonal recruitment of the invasive tree Psidium cattleianum: Implications for management of native Hawaiian forests. Biol. Conserv. 53, 199-211. Hawaii Volcanoes National Park Manipulative experiment and natural experiment
7647, (2015) Psidium cattleianum (Strawberry Guava). [online]. Available from: [Accessed March 10, 2015]. East Africa A descriptive factsheet of Psidium cattleianum invasion, with an emphasis on African countries.
7648 Lorence D. H., Sussman R. W. (1986) Exotic species invasion into Mauritius wet forest remnants. J. Trop. Ecol. 2, 147-162. Brise Fer and Bon Courage on the southwestern part of Mauritius Island Natural experiment/Measurative study
7649 Martin P. H., Canham C. D., Marks P. L. (2009) Why forests appear resistant to exotic plant invasions: intentional introductions stand dynamics and the role of shade tolerance. Front. Ecol. Environ. 7, 142-149. Global Review paper
7650 Morin L, Aveyard R, Lidbetter J. (2011) Myrtle rust: host testing uunder controlled conditions. NSW Department of Primary Industries, West Pennant Hills, NSW, Australia. NA Manipulative experiment
7651 Shiels AB., Ennis MK, Shiels L. (2014) Trait-based plant mortality and preference for native versus non-native seedlings by invasive slug and snail herbivores in Hawaii. Biol Invasions 16, 1929-1940 Hawaii Manipulative experiment
7652 Wikler, C., Pedrosa-Macedo J. H., Vitorino M. D., Caxambú M. G., Smith C. W. (2000) Strawberry guava (Psidium cattleianum) – Prospects for biological control. pp. 659-665. In: N R. Spencer (eds.) Proceedings of the X International Symposium on Biologic Brazil A review of the results of controlled experiments (specific methods found in lead author’s thesis in the references).