288 THE FRUIT GARDEN 



berries, healthy growth is arrested, the stalks lose their vitality, and the berries 

 become shrivelled and very sour. The primary cause of shanking wrill be 

 found in the stoppage of a proper flow of healthy sap. This may be caused by 

 a soil overcharged with organic matter, which condition, combined with bad 

 drainage, causes acidity of the soil ; the vine will then develop luxuriance 

 rather than maturity and ripeness of wood. It may be that the foliage has 

 been destroyed by red spider, invited by too dry an atmosphere and too high 

 a temperature. A never-failing remedy for shanking is to raise the roots and 

 relay them in new compost composed of good virgin turf. 



Mildew [Peronospora viticola). — This fungus causes two forms of disease. 

 If the leaf is attacked the disease is called downy mildew ; if the fruit, it is 

 known as brown rot. Leaves affected by this fungus show upon their upper 

 surfaces spots of a greenish yellow colour, while on the under side of the leaf 

 opposite these spots may be seen a peculiar downy or frosty growth. These 

 spots may be quite small and few in number, or very abundant, the frosty 

 growth almost covering the lower surface. When the fungus is abundant, the 

 leaf soon yields to the disease, turns brown, and falls from the vine. In severe 

 cases the disease extends to the young branches. The attack upon the fruit is 

 generally early, causing many of the berries to cease growing, turn brown, and 

 fall off. In treating grapes for this disease, Bordeaux mixture may be used with 

 good effect. Early washing of the vines is of advantage in freeing them from 

 spores which may have found lodgment in the crevices of the bark. 



Powdery Mildew [Uncinula spiralis). — This disease usually makes its 

 appearance about the middle of summer. It attacks the leaves, young shoots, 

 and fruits, covering them with a powdery growth. It differs from the downy 

 mildew in covering the upper surfaces of the leaves with white patches of 

 various size and shape. Sometimes it spreads quite early over the surface and 

 resembles a delicate spider's web. It does not send filaments into the tissues of 

 the host plant, but taps the epidermal cells with numerous minute suckers, and 

 through these saps the adjoining cells, while all the filaments are spread over the 

 surface of the leaf. The fruit when attacked shows upon the surface a whitish 

 dust. This rapidly spreads, and soon the berries shrivel and the skin cracks, 

 admitting other spores of decay, which complete the destruction of the fruit. 

 Being confined to the surface, this disease yields to the application of almost 

 any fungicide, but flowers of sulphur is probably the best. 



Insect Pests 



Red Spider {Tetranychus telarius). — With the exception of the phylloxera, 

 red spider is the most general and troublesome pest of the vine. It is not a 

 true spider, but belongs to what are called spinning mites. It has a difficulty 

 in moving on perfectly smooth surfaces, but by means of its claws and the 

 pin-headed bristles with which they are furnished, it moves readily on the 

 under sides of the leaves, and fastens its threads to the hairs or slight prominences, 

 thus gradually forming a coating of web, among which it lays its eggs, and 

 under this shelter a colony increases with alarming rapidity, especially if the 



