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Hellebore black death is a serious disease of hellebores, probably caused by the virus Helleborus net necrosis virus (HeNNV), where plants become stunted, deformed and marked by black streaks and ring patterns.
Hellebore black death
The disease known colloquially among hellebore growers as ‘black death’ causes stunting, distortion and black streaking and netting patterns on the leaves. It is probably caused by a newly described virus called Helleborus net necrosis virus (HeNNV).
In the UK, the most seriously affected hellebore is Helleborus × hybridus (syn. H. orientalis) but similar symptoms have been seen in other species. New damage can be expected from mid-spring.
You may see the following symptoms:
There are no chemical controls for plant virus infections.
Control of aphid vectors is not feasible with the products available to amateur gardeners because these are non-persistent and would need to be applied at unrealistically short intervals to give any protection against the arrival of winged aphids.
This disease has been recognised for about two decades in the UK, but is becoming progressively more serious. It is also known from mainland Europe and North America. A newly identified species of virus, Helleborus net necrosis virus (HeNNV), is associated with the disease, which is thought to be transmitted by the hellebore aphid, Macrosiphum hellebori. However, conclusive evidence for both suspicions is still lacking.
Aphids transmit viruses by feeding on the sap of plants with virus infection, and thus contaminating their mouthparts with virus particles. When they fly to healthy plants and begin to feed, they then infect the plant with virus. Seriously infected plants are so stunted they are unlikely to be attractive to aphids and the most dangerous plants are probably those which are still lightly infected and suitable for aphid feeding.
Symptoms not be confused with the general blackening caused by Botrytis cinerea or leaf spotting caused by Microsphaeropsis hellebori.
Hellebore aphidHellebore leaf minerHellebore leaf spotHelleboresPlant viruses
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