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Species Page

Japanese apple rust

Gymnosporangium yamadae
This information is part of a full datasheet available in the Crop Protection Compendium (CPC). Find out more information on how to access the CPC.
©CAB International. Published under a CC-BY-NC-SA 4.0 licence.

Distribution

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Extent
Invasive
Origin
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Host plants / species affected

Main hosts

show all species affected
Juniperus chinensis (Chinese juniper)
Juniperus chinensis var. kaizuka
Malus domestica (apple)
Malus prunifolia (plum-leaved crab apple)
Malus toringo (toringo crab-apple)

List of symptoms / signs

Leaves - abnormal colours
Leaves - abnormal forms
Leaves - abnormal leaf fall
Leaves - fungal growth
Leaves - honeydew or sooty mould
Leaves - wilting
Stems - canker on woody stem
Stems - galls

Symptoms

On Juniperus chinensis, G. yamadae causes fusiform swellings on stems that can produce telial horns under wet conditions. On apple [Malus spp.], the most conspicuous symptoms are the appearance of the aecia and pycnia on the leaves. On susceptible cultivars, G. yamadae can cause very severe defoliation. Infections on fruits are rare.

Prevention and control

Other Gymnosporangium species can be adequately controlled on apples by routine fungicide applications (for example, sterol-inhibiting fungicides), and this probably applies to G. yamadae. In Japan, G. yamadae was mentioned among the most important target pests for a new triazole fungicide (Ohyama et al., 1988). Mepronil can be used to control the disease on juniper [Juniperus] (Harada and Sawamura, 1980). In China, integrated management systems are proposed (Guo, 1994).

Most economically important apple cultivars are resistant to species of Gymnosporangium including G. yamadae as determined through inoculation experiments (Lee and Lim, 1984; Ha and Shim, 1995). However, eight apple cultivars including Fugi apple, a favourite cultivar in Asia, had a 35.5% infection rate, whereas other apple cultivars have a 15-20% infection rate (Lee and Lim, 1984). Sinclair and Lyon (2005) reported a summary of the junipers resistant to cedar-apple rust.

Suppression of the alternate host (Juniperus chinensis) within a certain radius of orchards is recommended, but may be difficult as it is often present in private gardens.

As infection of Juniperus is systemic in stems and evergreen leaves, no chemical treatment is likely to be completely effective to treat imported plants found to be infected. It is most unlikely that infection from the telial stage could be carried on packing materials and the risk is virtually confined to infected plants.

Countries should prohibit importation of plants for planting and cut branches of J. chinensis from countries where G. yamadae occurs, unless they are held in quarantine for a full growing season and found free from G. yamadae. Plants for planting and cut branches of Malus from the Far East should be dormant and free from leaves.

Impact

The rust is an important pest of apple in northern Japan, causing defoliation.