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Plum Rust



P_plumrust1

Plum Rust

Usually appear in

Summer to Autumn


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Caused By:-     The Fungus Tranzschelia pruni-spinosa

Description

This picture shows the top of one leaf at the end of summer. The yellow-orange spots are not as clear as it could be. The damage area is a by-product of the fungus. The top of leaves become discoloured by yellow-orange spots found in mid-summer onwards. The underside of the leaf is covered with numerous brown/black markings. In extreme cases the whole tree will be affected and the leaves fall early. The fungus is encouraged by damp weather and spreads throughout the leaf producing small spore producing black pustules on the undersides of the leaves. The same fungus affects both plum and anemones, it may be that the fungus overwinters on fallen leaves, which then infect anemones in spring and its the spores from these leaves that then reach and infect the plum I do not believe this as I do not grow anemones near my plum tree. Some over wintering may occur within plum bud scales.
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, Pelargonium, Periwinkle, Potato Internal, Quince, Rhododendron, Rose, Rust, White.


Control

This disease is common and widespread. Consistent attacks may weaken the tree. Remove and burn fallen leaves. Remove any affected anemones. The cultivar 'Victoria' is particularly susceptible to this fungus. Spraying with fungicide reduces the attack, but because the diseases is so widespread it will be re-infected if spraying is not continued on a regular basis. 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_plumrust1 P_plumrust2

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