Greenhouse Roses - pests of roses under glass

Chapter 22 (extract 2) of "Roses for English Gardens" by Jekyll and Mawley (1902), in which Mr Mawley notes the special challenges that pests pose when roses are grown under glass.

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Illustration: Mildew on rose (from Foster-Melliar "The Book of the Rose" 1894).

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Insect and other Pests.—As with such pests in the open ground, so with those in the house, prompt measures are the only safeguard. The three great enemies of the Rose under glass are aphides or greenfly, red spider, and mildew.

Aphides can be readily kept under by fumigation, which should be carried out the evening after the first greenfly is met with, and the dose repeated on the following night. A careful watch should be kept for the reappearance of this pest, and the same plan followed as before. If these directions be only faithfully carried out, greenfly will give little trouble. Richards' X.L. All vaporizing Liquid, or other similar preparation of nicotine, used according to the instructions supplied with it, will be found simple, cleanly, and effectual.

Red Spider.—This usually appears in spring when the air in the house has been allowed to become too dry. In order to destroy this pest the under side of the foliage should be frequently syringed with clear water, and at the same time the plants should not be allowed to become dry at the roots. In addition to this the hot-water pipes should be smeared with sulphur made into a paste by the addition of a little milk.

Mildew.—This is the most troublesome enemy of all to deal with in a Rose house if once allowed to establish itself, but if dealt with very promptly it can readily be kept in check. It most frequently arises from injudicious ventilation causing cold draughts of air to descend upon the tender foliage, for although

Roses like a buoyant atmosphere they soon suffer if exposed to a cold current of air, and more particularly if the house has previously been kept too hot or too close. The two great safeguards against mildew are judicious ventilation, and coating the water pipes with sulphur as recommended for red spider as soon as the plants come into leaf. This coating should be renewed about once a fortnight, for nothing will prevent the spores of mildew from finding congenial resting-places more effectually than the fumes of sulphur. However, notwithstanding all these precautions, should the slightest trace of mildew be seen, the plants affected, as well as the plants near them, should be at once dusted over with flowers of sulphur.

Rose Grubs.—In the early stages of growth these should be sought for and destroyed as soon as detected, hand picking being the only effectual remedy. But these pests will not be found nearly as numerous as in the case of Roses grown in the open air.

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More: Greenhouse Roses - roses in pots; summer treatment and repotting; forcing roses for winter flowering; roses in greenhouse beds; climbing roses under glass.

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