*NOTE: This plant disease is NOT KNOWN to occur in the US or in Texas.
COMMON NAME: Acacia Rust
SCIENTIFIC NAME: Uromycladium tepperianum
This disease is only found on Acacia spp. in Asia, New Zealand and Australia. The pathogen is not found in Texas or North America, and should not be confused with the Ravenelia fungus depicted on the calendar. There are many exotic pathogens found worldwide that threaten crops and trees if they were introduced into the U.S. For this reason, great efforts are made through quarantines, inspection stations, and other regulatory measures through the United States Department of Agriculture to prevent their introduction.
The most characteristic symptoms of this disease are large irregularly sized galls on stems, branches, phyllodes, and flowers. When young, these galls are light brown and becoming dull-brown with time. The galls size, shape and location on the plant varies according to the host attacked. Sometimes, infected plants are covered with masses of shoots, named witches’ brooms on branches.
The spores are spread by wind, and after germination, they infect the tree using natural openings. These spores will colonize the surrounding affected and induce the tree to produce galls from hormones released by the fungus or witches’ broom formation. During winter the fungus produces spores, dying on summer and ceasing the spore production. However, some galls can survive and produce some spores in the following year. For germination to occur, this pathogen requires freely available water on the plant surface and temperature between 10°C to 20°C.
- Regularly check plants especially when the climate favors the disease.
- Plant resistant varieties if available.
- Remove infected plants in the nursery destroying the affected areas.
- Fires or properly clearing operations may destroy locally the gall rust fungus, but after some years they can reinvade the area. For saving money during clearing operations, doing a chemical treatment of the cut stumps for many years to reduce the number of seedlings that germinate.
- Apply systemic fungicides during high-risk periods.
This factsheet is authored by Janaina Camara Siqueira da Cunha (PhD student)
Factsheet information for the plant health issues represented by the images on the 2019 TPDDL calendar were written by graduate students enrolled in the Department of Plant Pathology & Microbiology PLPA601 Introductory Plant Pathology course in the 2018 Fall semester (course instructor: Dr. David Appel). This exercise provides an opportunity for a high impact learning activity where the students are tasked with producing an informational output directed to the general public and to provide opportunity for the students to write.
*There are a number of rust diseases on Acacia that are not found in the US. A number of those are not consequential or highly detrimental to the tree, but there are those such as described species above are destructive to the plant. To learn more about those rust, check this information from our colleagues from New Zealand.( http://www.nzffa.org.nz/farm-forestry-model/the-essentials/forest-health-pests-and-diseases/forestry-diseases/Uromycladium/UromycladiumPath15/) -KO