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Juniper Pear Rust


Juniper Pear Rust

Usually appear in

Spring to Autumn.

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Caused By:-     The Fungs Gymnosporangium sabinae


The fungus on pear leaves.
Pear Juniper Rust is caused by the rust fungus Gymnosporangium sabinae(G. fuscum). Like most rust diseases it requires two different host to complete its life cycle from year to year. With this fungus juniper is the winter host and pear is summer host. Spores (Called Aeciospores) are produced from the fungal lantern-shaped growths which protrude from the blisters on the underside of the pear leaf which become airborne and infect junipers. This fungus overwinters in swellings or galls on infected twigs and branches of susceptible juniper plants. In the Spring after a rain or heavy dew, the galls on the juniper produce tiny dark horn-like growths that become covered with an orange-brown gelatinous mass called telia. The corresponding stage on the pear trees is known as aecia. The telia and aecia release wind borne resting or hibernating spores (called Teliospores and Aeciospores) capable of infecting susceptible pear leaves and Juniper respectively. Spores produced from the fungus-induced swellings on juniper stems can be infectious up to 6km. The disease causes a yellow-orange spot that turns bight red on leaves of pear trees(Pyrus). The disease can be particularly damaging on pear, resulting in complete defoliation and crop loss if not treated. The fungus feeds on the living cells of the host plant and is not capable of surviving on dead plant material, so must either alternate with a different host, or produce resting spores to pass the dormant season. Pear rust is a regulated disease in some countries.
See also these other rusts Anemone, Antirrhinum, Bean, Bluebelle, Broad Bean, Cedar Quince, Chrysanthemum White, Fucshia, Gladiolus, Gooseberry, Hollyhock, Mahonia, Mint, Pear Juniper, Pelargonium, Periwinkle, Plum, Potato Internal, Quince, Rhododendron, Rose, Rust, White.


It is important to break the disease cycle and remove infected leaves as soon as the fungus is seen.
Prune out any infected Juniper twigs and branches in winter and early spring, if possible, about 15cm below the infected area . The vulnerable point of attacking this fungus lies in the inability of the fungus produced on one tree to reinfect it. It must pass to the opposite host. The most direct method of control is to exterminate Junipers near the Pryus trees.
If there is a chance of infection spray the Pyrus with a fungicide preferably a systemic one in Spring and Summer that is certified as capable of dealing with Rust.
spraying the tree with a winter fungicidal wash in the dormant period.
In the European Community the products permitted under organic regimes have little effect rusts. Fungicides containing myclobutanil (Bayer Garden Systhane Fungus Fighter and other formulations), penconazole (Westland Fungus Attack) and triticonazole (Scotts Fungus Clear Ultra) can be used to control rust, but care should be excercised when using these fungicides.
The fungus is encouraged by high humidity with a lack of air circulation.
It overwinters on old plant materials so these should be burnt.
Spraying with a suitable fungicide is necessary and must be carried out several times.
As with any fungal disease one of the best ways of preventing it is by good hygiene. Remove all dead leaves in autumn to prevent the spores from over wintering. If the leaves is from an infected plant burn them.
Check plants regularly and remove infected leaves by hand as soon as they are seen and then spray with a suitable fungicide. Spray the plant and the soil around it with a fungicide suitable for the control of rust fungus.
Water the compost of susceptible plants directly trying not to wet the foliage as the rust needs a period of leaf wetness to germinate and infect.
Watering the soil in the dormant season with Jays fluid or Amarillotox should also help. In some Countries these products are not licensed for this use.
Maintain an open structure to allow good air circulation through the plant and ensure greenhouses are always well ventilated. Often there are resistant varieties of the plant you wish to grow.
Avoid over application of nitrogen, which produces soft growth which is more susceptible and ensure adequate potassium fertiliser.

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