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Escallonia is a reliable, hardy, flowering shrub suitable for use as specimen plants or as hedging. Until recently it has been free from foliar disease problems but now a fungal disease causing leaf spots and defoliation is causing concern.
Escallonia leaf spot
Escallonia leaf spot is a fungal disease of Escallonia, causing spotting on the leaves followed by defoliation. It was only first noticed a few years ago but has since spread rapidly. Severely affected plants can be reduced to bare branches.
You may see the following symptoms:
There are no fungicides available to amateur gardeners with specific recommendations for use against escallonia leaf spot. However, the fungicide tebuconazole with trifloxystrobin (Bayer Fungus Fighter Plus) carries a label recommendation for use against 'leaf spots' on ornamental plants. Tebuconazole (Bayer Fungus Fighter Concentrate) and triticonazole (Scotts Fungus Clear Ultra and Scotts Fungus Clear Ultra Gun) are labelled for the control of a number of other diseases on ornamental plants and could therefore be used legally on Escallonia (at the owner’s risk) to try and control leaf spot.
There is no specific information available as to the efficacy of these products against the leaf spot, however. It is likely that repeated sprays will be required where the disease is present, particularly during unsettled weather. Success is more likely if the plant is cut back hard to remove affected material, and then sprays applied to protect the new growth. It would be prudent to apply a small amount of the chosen fungicide first to ensure that the product will not cause plant damage.
Inclusion of a fungicide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.
Fungicides for gardeners (Adobe Acrobat pdf document outlining fungicides available to gardeners)
Chemicals: using a sprayerChemicals: using safely and effectivelyChemicals: storing and disposing safely
Examination of samples received by the RHS has shown that two different fungi may be associated with the leaf spots (although they are never found together in the same spot). The first, and by far the most common, is a Septoria species. This produces the tiny black fruiting bodies described above – under wet conditions colourless tendrils of spores ‘ooze’ from these fruiting bodies. Occasionally, a Cercospora species can be found instead – this produces ‘tufts’ of spores rather than black fruiting bodies. Work is currently being undertaken by the RHS Plant Pathology department in collaboration with Royal Botanic Gardens Kew and the University of Reading into the precise identification of the species of Septoria and Cercospora involved.
Many fungi produce asexual and sexual types of spore at different stages of their life-cycle. Unfortunately, the fungus is often given a completely different scientific name depending on what type of spore it is producing, which can be very confusing! Both Septoria and Cercospora species produce asexual spores. In each case, if the fungus were to produce sexual spores it would be known as a Mycosphaerella species. Although these sexual spores have yet to be found on affected leaves, the disease is therefore usually referred to as Mycosphaerella leaf spot.
As this is a relatively new problem the precise conditions for spread of the disease are unknown, but it is certainly favoured by wet weather conditions. Spores are likely to be splashed around by rain droplets, germinating to set up new infections if the leaf surface stays wet for an extended period. The fungus probably persists on fallen leaf debris.
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