Several pests vex the gardener in growing grapes indoors. Of these, mealy-bug, red-spider, thrips and mildew are most troublesome. In a well-conducted grapery, there is never an intermission in the warfare against these pests.
Mealy-bug is usually a sign of sloth on the part of the gardener. In a grapery devoted exclusively to grape-growing, it should never be seen, but, since gardeners must often grow other plants in the grapery, mealy-bug sooner or later appears and is often hard to dislodge. It is best repelled by removing the loose bark on the trunks which harbor the pest and then washing with kerosene emulsion. When this becomes necessary, not only the vines but the rafters and all parts of the house should be sprayed with the emulsion.
Red-spider is another pest usually found in the grapery, but it thrives only in a dry atmosphere and is easily gotten rid of by syringing. As soon as red-spider appears in a house its appearance is usually known by the reddish tinge on the foliage; syringing should be kept up until the pest is disposed of, keeping the house damp in all except dull weather. Syringing is done only when plenty of air can be given and when it can be followed by sunlight so that the water remains on the vines as short a time as possible.
Thrips, another small insect, is sometimes troublesome but not often and is now easily controlled by applications of nicotine. Much care must be taken in the application of nicotine late in the season, otherwise the fruit will be injured.
The only fungous disease of the grape troublesome in the greenhouse is mildew. Mildew is usually brought on by a sudden change of temperature or by draughts in the grapery. Gardeners are of the opinion that east winds, in particular, give unfavorable conditions for mildew and prefer to open the ventilators to the west. If taken in time, mildew is easily kept in check by preventing the conditions which favor it, and by dusting the vines in dry sunshine with sulfur.
Plate XVI.—Elvira (×2/3).