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Pansy Downy Mildew


Pansy Downy Mildew

Usually appear in

All Year

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Caused By:-     The fungal-like organism Peronospora violae


Downy mildew of pansies is a fungal-like disease caused by Peronospora violae(Bremiella megasperma). It causes pale blotches on the upper surfaces of the leaves and fuzzy grey mould growth on the underside of leaves. Eventually the whole leaf dies from the fungus-like organism which lives within the tissues of the leaves whilst extracting nutrients.
When the infected leaf tissues eventually die, it forms resting spores in the dead material which will then contaminate the soil. If it is sprayed in the early stages only some of the tissues will die and the leaves will be scarred. The youngest leaves and shoots are especially susceptible to the fungus. The white growth on the leaves are the spores which are carried by the wind or plashes from watering. Although with Pansies it is usually usually fatal.
The fungus overwinters on fallen leaves or as spores inside a chasmothecia which eventually breaks down to release the spores to infect other Pansies.
Downy mildews are usually host specific, which means they do not spread to other types of plants. There are many types of Downy Mildew fungi and they all produce similar symptoms. Infected leaves may become distorted, turn yellow with patches of green, and fall prematurely, stems may collapse and die and infected buds may fail to open.
The disease is usually observed on the under sides of the leaves with a whitish fungal growth developing on the leaf surfaces in patches which eventually coalesce to cover the leaves, stems or buds. The infected areas dies or may become soggy.
The severity of the disease depends on several factors such as variety of the host plant, age and condition of the plant. It is especially severe in cool humid climates and needs wet weather to moisten foliage for 2-4 hours and a temperatures of 10- 12°C in order for the spores to germinate and infect plants. Therefore if the relative humidity is high the problem will be worse. Crowded plantings where air circulation is poor damp and in shaded areas makes the problem worse. Young growth usually is more susceptible than older plant tissues.
Infected tissues are often colonised by grey mould like Botrytis cinerea and this can lead to further rotting.
See also Downy Mildews Brassica, Downy, Hebe, Lettuce, Onion, Pea.
See also other Mildews American Gooseberry, European Gooseberry, Gooseberry.
See also these other Powdery Mildews Apple, Begonia, Hydrangea, Oak, Pansy, Pea, Phlox, Powdery, Quince, Rose.


Remove infected leaves as soon as the discolouration on the upper surface is seen. This will prevent infected leaves from contaminating the soil. Also reduce humidity wherever possible. If possible do not grow pansies on the same site in consecutive years.
Spraying with fungicides is often ineffective as the infection is within the leaves therefore the only fungicides that may have an effect is a systemic type.
Baking Soda, Bicarbonate of Soda, is said to be preventative treatment for most any fungal infection, and is not harmful to the soil. It works best in the early days of infection, and should halt downy mildew. Dilute about 6 teaspoons in a litre of water, and spray on, covering the whole plant, and even the soil around. re-spray after 2 weeks, as a further preventative measure.
Spraying with a mixture of baking soda(sodium bicarbonate) or potassium bicarbonate combined with a lightweight horticultural oil is said to cure and prevent the problem.

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