Two fungal pathogens of camellias cause brown leaf blotches, premature leaf loss and twig or branch dieback. They are most damaging on young plants or newly propagated material.
What is camellia leaf blight?
Camellia leaf blight is a disease that can be caused by two fungal pathogens: Monochaetia karstenii or Pestalotiopsis species. 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 causal 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 completel
N.B. Camellia leaves may also develop brown patches as a result of frost damage in spring, or sun scorch during hot summers. In these cases the symptoms will often develop quite rapidly on several leaves at the same time, and fungal fruiting bodies won’t be visible.
The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods,
cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.
- Good hygiene can help, as do cultural control measures. These include removing affected leaves, twigs or
cuttings promptly and destroying 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 use against camellia leaf blight. However, the fungicides tebuconazole (Provanto Fungus Fighter Concentrate) and tebuconazole with trifloxystrobin (Provanto Fungus Fighter Plus, Toprose Fungus Control & Protect) are labelled for the control of leaf spots on ornamentals, whilst triticonazole (Fungus Clear Ultra) is labelled for the control of other diseases on ornamental plants. These products may give some control of leaf blight on camellia.
The following products contain a combination of both insecticide and fungicide, enabling the control of both insect pests and disease: myclobutanil containing cypermethrin (Resolva Rose 3 in 1, Rose Shield Bug & Fungus Killer, Roseclear Ultra Gun 2, Rosegarde) and triticonazole containing acetamiprid (Roseclear Ultra, 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.
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.
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