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Arbutus are evergreen trees or shrubs, some of which also produce attractive red fruits. They can sometimes be affected by fungal leaf spot diseases, which may spoil their appearance and, in severe cases, lead to leaf loss and twig dieback.
Leaf spots on arbutus are usually caused by one of two fungi. Elsinoë mattiroloanum is the more common and damaging, may be found on twigs as well as leaves, and can lead to leaf loss and twig dieback. Attacks by Ruptoseptoria unedonis are usually confined to the leaves.
You may see the following symptoms:
There are no fungicides available to amateur gardeners with specific recommendations for use against leaf spots on arbutus. However, the fungicides tebuconazole (Bayer Fungus Fighter Concentrate), tebuconazole with trifloxystrobin (Bayer Fungus Fighter Plus), and triticonazole (Scotts Fungus Clear Ultra and Scotts Fungus Clear Ultra Gun) are labelled for the control of other diseases on ornamental plants, and could therefore be used legally on arbutus (at the owner’s risk) to try and control the leaf spotting.
There is no specific information available as to the efficacy of these products against arbutus leaf spots, however. It would be prudent to apply a small amount of the chosen fungicide first, at a solution suggested on the packet for other problems, 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
The development of each of these diseases is likely to be favoured by wet weather conditions. Ruptoseptoria unedonis produces large numbers of microscopic spores from tiny fruiting bodies within the spots. The spores are splashed around by rain droplets and will infect if the leaf surface remains wet for an extended period. Little is known about the life-cycle of Elsinoë mattiroloanum.
As arbutus is an evergreen plant the fungi may be present on the leaves year-round, but could also potentially overwinter on fallen leaf debris or, in the case of Elsinoë, in lesions on the twigs.
Coral spotDisposing of diseased materialEscallonia leaf spotPyracantha scabTree and shrub: scab diseases
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