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Grey Mildew is a pathogen
which effects a large number of plant species, among which the Gerbera
unfortunately is one of the most susceptible, especially in periods or
very damp cultivation conditions. From this point of view it is
undoubtedly one of the diseases that limits the cultivation of the Gerbera
in many areas. The disease typically causes a "soft rottenness"
on all leaves that are covered with large amounts of it. |
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Grey Mildew under a microscope
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It consists of the multiplication or conidial forms of the fungus.The mycelium and sclerotium are their resting structure,
these live in the foliage remains on the soil, or on wild plants.
Botrytis spores contain very little water so they depend on the dampness of the environment. They germinate extremely well even in
thin layer of free water. Especially if it contains sugar. Thus, condensation on leaves is perfect. A short dry period does not harm
the germinating spores, but longer periods of dry conditions will dry them out and kill them.
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When the leaves are wet and the temperature is 15-25 C, the spores germinate and grow. They form mycelium threads that penetrate
the leaves, which marks the start of an infection. Once the disease is established it forms new spores, especially under humid conditions.
Spores are released when the spore-bearing plant material is disturbed or when the relative humidity changes rapidly.
Under normal conditions unless an abundant inoculation source is available, the fungus is incapable of attacking vital organs and in active
development.
These in fact, are damaged only if they are come into contact with an organ already infected with abundant grey mildew.
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| Young Gerbera attacked by fungus |
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The pathogen develops in abundance on old organs, producing a big quantity of enzymes that damage
the adjacent vegetable tissue and facilitate the invasion of the fungi mycelium.
On young Gerbera plants, the rottenness produced at
the base can cause their death.
On the flower, the most characteristic symptom is the appearance of brown sunken spots of various dimensions, when climatic conditions
are not too negative, they are not visible to the naked eye.
The infection is encouraged by temperature between 4 and 32 C, but occurs especially when relative humidity levels are higher than 85-90%.
The spread of the pathogen takes place through water and air.
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Brown spots on a flower |
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| Return to the top of Grey Mildew |
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