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Chrysanthemum White Rust



P_chrysantwhiteblight

Chrysanthemum White Rust

Usually appear in

Spring to Autumn


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Caused By:-     The Fungus Puccinia horiana

Description

Chrysanthemum white rust is a serious disease of chrysanthemum which spreads very quickly covering the plants with pustules. It is a quarantine disease in some countries. It produces small white to yellow spots up to 4 mm wide on the upper surface of the leaf. These may be slightly raised. These spots become brown over time. Pustules form on the underside of the leaf, beneath the spots which can distort the leaves. The spots first appear as creamy-coloured. As they age, they become white. Pustules are most common on young leaves and flower bracts but can be found on any part of the plant including flowers. Picture by Central Science Laboratory, Harpenden Archive, British Crown, Bugwood.org.
See also these other rusts Anemone, Antirrhinum, Bean, Bluebelle, Broad Bean, Cedar Quince, Fucshia, Gladiolus, Gooseberry, Hollyhock, Juniper Pear, Mahonia, Mint, Pear Juniper, Pelargonium, Periwinkle, Plum, Potato Internal, Quince, Chrysanthemum White, Rust, Rhododendron, White.


Control

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. Rotate bean with non-host crops.
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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