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White Rust



P_whiterust

White Rust

Usually appear in

Summer


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Caused By:-     Fungus species of the Genus Albugo

Description

White rust is a chronic foliar disease problem for several plants especially of the brassica, spinach and other plants. It is caused by the fungus Albugo candiada and there are several species in this Genus that tends to attack specific plants.
The fungus persists in soil as resistant spores that can survive for many years and initiate primary disease infection. Secondary disease infection comes from airborne spores. It prefers temperatures between 20 to 30 degrees centigrade and wet weather. The spores enters the leaves via the stomata in the leaves and therefore mainly appears on the underside of the leaves. The fungus attacks all the above ground parts of the plant and the roots are not affected. The disease produces white, blister?like pustules on the lower leaf surface of leaves. Tissue surrounding the spore?filled pustules later turns brown and dies.
White rust differs from the true rusts in not requiring an alternate host.
Another disease called White Rust is Chrysanthemum White Rust which is caused by the fungus Puccinia horiana.
According to Wikipedia there are several synonyms:- Aecidium candidum Pers., (1797), Albugo cruciferarum (DC.) Gray, (1821), Cystopuscandidans, Cystopus candidus (Pers.) Lev., (1847), Uredo candida (Pers.) Fr., (1832), Uredo candida Rabenh, Uredo cruciferarum DC.
See also these other rusts Anemone, Antirrhinum, Bean, Bluebelle, Broad Bean, Cedar Quince, Chrysanthemum White, Fucshia, Gladiolus, Gooseberry, Hollyhock, Juniper Pear, Mahonia, Mint, Pear Juniper, White. Pelargonium, Periwinkle, Plum, Potato Internal, Quince, Rhododendron, Rose, White. Rust.


Control

To control Spinach White Rust fungicides need to be applied several times during the growth of the plants. It is also advisable to use several types of fungicides and in winter soak the soil with a soil sterilant.
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.
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.

P_whiterust P_whiterust2

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