Enemies of the Rose - fungus (mildew, rust)

Chapter 20 (extract 3) of "Roses for English Gardens" by Jekyll and Mawley (1902), in which Mr Mawley describes the treatment of mildew, one of the most troublesome rose diseases, with sulphur.

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Illustration: Rose Mrs Mawley (Tea)

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Fungoid pests—Mildew.—Of all the insect and fungoid enemies of the Rose this is, as a rule, the most troublesome to deal with. It appears as a white mould on the foliage, and if not promptly dealt with will quickly spread from one plant to another over the whole collection.

It occurs at all seasons, but principally in autumn, when, if not checked, it will prevent the plants from flowering as freely as they otherwise would. Flowers of sulphur is a sure preventive, but each attack must be dealt with on its first appearance, and the application repeated until a cure is effected. A very simple way of applying the sulphur is by shaking it lightly over the affected plants by means of a fine muslin bag the first calm evening after the mildew is detected. Although only the upper surface of the leaves are dusted over it will be found in practice that the action of the sun will vaporise the sulphur and cause the surrounding atmosphere to be impregnated with it. Syringeing or spraying with the following liquid will also prove effectual, more especially if the under side of the leaves can be wetted with it. To make this mixture half an ounce of potassium sulphide should be dissolved in a gallon of hot water, which should be well stirred as the sulphide of potassium dissolves; when cold the liquid will be ready for use. Warm days followed by cold nights are the most frequent causes of this pest, also a close, muggy atmosphere.

Red Rust or Orange Fungus.—This is much more variable than mildew, and in many gardens is seldom if ever seen, while in others, particularly those on hot and dry soils, it is frequently very destructive to the foliage in the autumn. On its first appearance a few sulphur-coloured spots will be noticed either on the leaves or shoots. In the next stage it increases and becomes a bright orange, ultimately turning black.

There is no practical remedy for this fungus, as unlike mildew it vegetates inside instead of on the surface of the foliage.

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More: Enemies of the Rose - frost and drought; insect pests