25 April 2010

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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