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Rust



P_rust1

Rust

Usually appear in

Usually Spring and Summer


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Caused By:-     Various Fungal spores

Description

This picture is of an Oxalis leaf with a 1cm ruler showing the orange pustules of rust. There are many different fungi that causes rust in various plants or trees. The name is very descriptive as rust often looks like a piece of iron going rusty. Often, but not always it is Orange-brown pustules that develop initially on the undersides of leaves. These may be unnoticed for some time, but there is usually a yellowing on the top surface of leaves, corresponding to the pustules on the underside, before the pustules appear on the upper leaf surface. Some rust only have one host whilst others are omnivorous as regards which plant to infect. Some need two host to complete their life cycle(like Berberis and Wheat) whilst others do not. It is not usually a killer, but is very unsightly and badly affected plants can be so weakened they are unable to withstand other stresses and diseases. Spores from the pustules can be transmitted between plants by the wind; on animals fur; by attaching themselves to insects or people's clothes and hands. The fungus is encouraged by a humid, moist conditions and grows on the surface of the leaves and sometimes stems taking its nutrition from the plant. Most rust have a 'latent' period of time, where the plant can be infected without showing any symptoms.
See also these other rusts Anemone, Antirrhinum, Bean, Bluebelle, Cedar Quince, Chrysanthemum White, Fucshia, Gladiolus, Gooseberry, Hollyhock, Juniper Pear, Mahonia, Mint, Pear Juniper, Pelargonium, Periwinkle, Plum, Potato Internal, Quince, Rhododendron, Rose, White.


Control

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. In greenhouses it is best to keep air circulation high and conditions on the drier side.
It overwinters on old plant materials so these should be burnt.
As with any fungal disease one of the best ways of preventing it is by good hygiene. Remove and burn 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, remove and burn 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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