Downy Mildew on Ornamentals
What ornamental diseases are particularly difficult to control?
Ornamental diseases caused by downy mildews are making headlines in the ornamental industry press, and my field observations in
The same fungus causes disease on all those plant species?
First, the downy mildews are caused by a group of fungus-like micro-organisms. They are not true fungi. When it comes to causing diseases however they have similar ways of causing infection and are controlled with similar tactics.
Actually the pathogens that cause downy mildew diseases on snapdragon, rose, foxglove, and delphinium are all different species. They all have specific and, in this case, different host ranges. For example the pathogen that causes downy mildew disease on rose will not cause downy mildew on snapdragon.
What do these diseases look like?
Disease symptoms vary greatly depending on the plant. Generally there can be gray to purplish fungus-like growth on the lower sides of leaves and this is often associated with leaf yellowing. Sometimes leaves drop from the plant, as they do commonly in roses. Click here -
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Anything else I should know?
Be on the lookout for a new downy mildew on marguerite daisy (Argyranthemum frutescens = Chyrsanthemum frutescens). This disease was observed in
We need your help to confirm the presence of this disease and identify the pathogen. Please report any suspicious observations.