These fungal diseases of camellias cause the leaves to brown, premature leaf loss and twig or branch dieback. They are most damaging on young plants or newly propagation material.
What is camellia leaf blight?
Camellia leaf blight is a fungal disease caused by one of two fungal pathogens: Monochaetia karstenii and Pestalotiopsis guepini. The development of the disease is favoured by wetness on the leaves and any factors that weaken or damage the foliage.
You may see the following symptoms:
- Discoloured patches develop on the leaves. These soon turn brown, giving the lesions a scorched appearance
- Numerous tiny, black fruiting bodies of the fungus develop over the surface of the lesion (damaged area). In wet or very humid conditions these may be seen to exude a black tendril of spores
- Infected leaves often fall prematurely. The infection can spread down the petiole and into the branch, leading to dieback. Affected cuttings may decay completely
- Good hygiene can help, as do cultural control measures. These include removing affected leaves, twigs or cuttings promptly and destroy them. Where possible, keep leaves dry to prevent dispersal and germination of the spores
- If pruning out affected twigs or branches, disinfect the pruning implement between each cut
There are no fungicides available to amateur gardeners with specific recommendations for the control of Camellia leaf blight. However, the fungicides difenoconazole (Westland Plant Rescue Fungus Control), myclobutanil (Bayer Garden Systhane Fungus Fighter and other products), tebuconazole (Bayer Garden Multirose Concentrate 2) and triticonazole (Scotts Fungus Clear Ultra) are labelled for the control of a number of other diseases on ornamental plants, and may give some control of Camellia leaf blight.
The following four products contain a combination of both pesticide and fungicide enabling the control of both insect pests and disease: myclobutanil containing cypermethrin (Westland Rose Rescue); tebuconazole containing deltamethrin (Bayer Garden Multirose 2), and triticonazole containing acetamiprid (Scotts Roseclear Ultra and Scotts Roseclear Ultra Gun). When a proprietary product contains an insecticide as well as a fungicide it would be preferable to use an alternative product if pests are not a problem on the plants treated.
Fungicides for gardeners (Adobe Acrobat pdf document outlining fungicides available to gardeners)
Chemicals: using a sprayer
Large numbers of spores are produced by the fruiting bodies. The spores are spread by water splash, and will germinate to create new infections if the leaf surfaces stay wet.
The fungi are generally regarded as weak pathogens, and are much more likely to colonise plant tissue that is damaged, dead or that has been weakened by stress factors.