What plants are affected?
The hosts of blueberry rust include Vaccinium spp. (blueberries and cranberries), Gaylussacia spp. (huckleberries), Rhododendron spp. (azalea) and Lyonia spp.
In Australia, blueberry rust has only been reported on blueberries. Southern Highbush varieties are more susceptible to the disease than other types of blueberries.
The complete lifecycle of blueberry rust is complicated, and in some environments the fungus can produce spores during five life stages. Conifer hemlocks (Tsuga spp.) are the alternative hosts which the rust needs to complete its lifecycle in colder climates. However in mild climates like Australia's, blueberry rust does not need an alternative host.
What do I look for?
- The first symptoms of blueberry rust are small reddish spots on the upper surfaces of young leaves.
- These lesions darken with age and are often surrounded by a yellow halo.
- On the undersides of the leaves, yellow pustules develop. Each pustule releases thousands of yellow spores which can infect other leaves and spread the disease.
- In severe cases, leaves turn brown, curl up and drop from the plant.
- Disease pustules may also appear on developing fruit later in the season.
How does the disease survive and spread?
- The thousands of spores released from the pustules are very easily and quickly transported by wind (up to several hundred metres), and can also be spread via infected plants and fruit, packaging, equipment, clothing and hands.
- The disease survives over winter on evergreen blueberry leaves, then develops in warm, wet conditions. The optimum temperature for production of spores is around 21°C, with new infections unlikely when the temperature is over 30°C.
- New pustules can be produced and release spores every 10-14 days.
- The spores are able to re-infect the original host plant as well as other blueberry plants and other host species.
What damage can this pest cause?
Blueberry rust causes poor fruit production and reduced vigour in blueberry plants because of the loss of leaves. Serious defoliation can lead to the death of susceptible varieties.
What do I do if I find it?
Thekopsora minima (Arthur) Syd. & P. Syd, 1915 is considered absent from Western Australia and is a quarantine pest.
It is a prohibited organism under section 12 of the Biosecurity and Agriculture Management Act 2007
Area freedom status for WA is supported by general and specific surveillance and phytosanitary measures (including import requirements and mandatory reporting and monitoring for the pest).