Escallonia falling victim to leaf spot disease
Escallonia is a very popular hedging shrub especially by the seaside. Native to Chile, it is an attractive plant with dark, evergreen leaves and flowers ranging in colour from pink to deepest red.
The trouble with it at present is that for several years now it has been plagued by leaf spot, a disease caused by a fungus or mould. The disease presents as spots on the leaves in early autumn. As autumn marches on into winter the affected leaves turn yellow, die and drop off leaving the normally evergreen shrub looking pretty miserable.
Teagasc researchers have recently identified the fungus that causes the leaf spot disease in Escallonia as a new species of Septoria.
Septoria is a very large genus or group of fungi the members of which are responsible for many different diseases. The group is estimated to contain more than one thousand species.
Escallonia comes as many different hybrids and cultivars. In my neck of the woods the broad-leaved forms appear to suffer most from the leaf spot disease. Many hedges have been severely set back; several have died.
Each year, in the plants that have survived, new growth comes fresh and disease free. All appears to be getting on well until August comes and the spots start to appear, small at first but spreading rapidly in damp weather. By Christmas hedges will be bedraggled.
Escallonia leaf spot causes diseased parts of the leaves to change colour resulting in a mosaic of live green bits, yellow diseased bits and brown dead bits. In wet weather tiny white areas may sometimes be seen in the dead brown tissue. These are where the fruiting bodies of the fungus are located.
The fungus produces spores and these are dispersed by rain. Spores overwinter in dead leaves. The following year, spores are leap-frogged around the hedge and upwards from the ground by rain splash. As long as the weather stays damp the fungus reproduces rapidly and spreads.
To break this cycle, gardening magazines advise tidying up all the dead leaves from under an infected hedge. While the advice makes sense in theory, actually doing it is nigh impossible when a wide old hedge is involved.
Researchers in the Teagasc Research Centre at Ashtown near the Phoenix Park in Dublin are continuing trials to find a fungicide to kill the disease and report that they hope to have results by early next year.