76 RATIONAL FRUIT CULTURE. 



Silver Leaf. — Plum, Peach, and other stone-fruits. The 

 leaves lose their green colour, and have a silvery appearance. 

 The death of the affected part, sometimes a single branch, 

 and sometimes the whole tree, follows. The disease can easily 

 be distinguished from chlorosis, as only the upper surface is 

 affected. It is due, not to the loss of chlorophyll, but to the 

 pressure of air under the skin. The cause is doubtful, and no 

 cure is known. A parasitic fungus, which stains the wood 

 red, and produces purplish or brown incrustations on the bark, 

 is frequently associated with the disease, but the association 

 is not invariable. As some authorities connect silver leaf with 

 excessive quantities of nitrogenous manure, this condition 

 should be avoided. 



Stem Disease. — Apple, Pear, Plum; sometimes other 

 stone-fruits. Attacks are confined to young trees, mainly in 

 clay soil, and especially when planted too deeply. The leaves 

 wither and fall early, and the bark shrivels, the small, narrow 

 cracks which appear in it containing the spores of the fungu^ 

 and spreading infection. In the following year there are 

 larger cracks, and the trees are soon killed. To prevent the 

 spores from germinating in the cracks, paint the stem with 

 soft soap, reduced to the consistency of thick paint by means 

 of a strong solution of washing soda, with the addition of one 

 pound of powdered quicklime to every five gallons. Badly^ 

 diseased trees should be grubbed up and burned. 



Tree-Root Rot. — Nearly all orchard trees. The leaves 

 droop and turn yellow, and if some bark is removed near the 

 base of the tree a wliito felt of inyeolium will probably he 

 si^eri Underneath. At this stage the ease is hopi^Iess. The 

 fungus is rather a large toadstool, brown ish-yel low, with 

 small, dark scales, the stem simila,rly coloured with a frill 

 near the top. It giows in clusters round the roots. As the 

 disease does not show itself until i( is [iiai-lically incurable, 



