What is it?
This is a fungus like organism that causes the disease. All stages of the pathogens life cycle are of concern including the active reproductive stages and the relatively long lived spores that can survive in the soil and plant debris. The longevity of viable spores could also lead to greater genetic variability as time goes on.
Where it can be found
The disease has been found in historic gardens, public parks, woodland and heathland environments, plant nurseries and garden centres. The symptoms appearing mainly on shrubs such as Rhododendron, Camellias and Viburnum while the trees showing symptoms include Beech, Horse chestnut, Larch and Magnolia. This list indicates those species known at present, it is feared more plant types will also succumb.
What are the symptoms?
These vary slightly between plant groups. Shrubs can show blackening of leaves around the midrib and the tips and/or wilting and dieback of their younger shoots. Trees can show black lesions on the bark which can ‘bleed’ black sap. Heathland plants can suffer severe dieback of the entire plant.
How does it spread?
The microscopic spores produced on infected plants are spread in water splashing onto uninfected leaves and in surface water runoff caused by rain or irrigation. Also on any soil picked up on footwear or the feet of animals walking through infected areas. Taking cuttings or moving infected plants and infected material is also a method of spreading the disease to new areas.
We can all help to reduce the risk of spreading this disease by following good practice every time we are involved in the outdoor environment. The Food and Environment Research Agency are encouraging us all to follow these guidelines –