Pacific Pests, Pathogens & Weeds - Fact SheetsKauri rust (236)
Common Name
Kauri rust
Scientific Name
Aecidium fragiforme
Distribution
Narrow. Southeast Asia and Oceania. It is recorded from Australia, Fiji, New Caledonia, Solomon Islands, and Vanuatu.
Hosts
Agathis species (kauri).
Symptoms & Life Cycle
The fungus forms raised galls, up to 20 mm diameter, and 5 mm high (Photos 1). The lower surface is often depressed. White to yellow pustules are formed within the galls, usually on the upper surface of the leaf (Photo 2). The pustules contain spores of the rust fungus.
There are two types of spore-forming structures that occur on the raised spots or galls: pycnia and aecia. The pycnia are small, 0.1 diameter. They produce spores which are exchanged - a form of mating - between pycnia, probably by insects. This "mating" produces the aecia, which are much larger, 1 mm diameter (Photos 1&2). From aecia, aeciospores form, and these are spread in wind and rain to infect other parts of the same leaf, other leaves, or other trees.
Impact
The galls are more common on younger plants, sometimes causing leaves to fall. However, this is not an important disease, although details of its impact are not well reported.
Detection & inspection
Look for raised yellow spots on the leaves becoming reddish brown, circular, up to 2 cm diameter.
Management
There is no treatment for this disease.
AUTHOR Grahame Jackson
Photos 1&2 Kohler F, Pellegrin F, Jackson G, McKenzie E (1997) Diseases of cultivated crops in Pacific Island countries. South Pacific Commission. Pirie Printers Pty Limited, Canberra, Australia.
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.
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