516 



STONE FRUIT. 



Almonds, apricots, peaches, and nectarines, as well as plums 

 and cherries, are attacked by fungus diseases, which, if not in 

 every instance identical, are sufficiently closely related to be 

 described under one heading, and are amenable to similar treat- 

 ment. 



CURL LEAF (Exoaseus deformans, Eckl.). Sometimes simply 

 called the "curl," owing to the leaves becoming distorted and 

 crumpled, early in the season. After a time a delicate whitish 

 bloom, caused by the spores of the fungus, show on the surface. 

 The young shoots are also at times swollen and distorted by the 

 fungus. 



When the attack is bad, the trees at times lose their leaves 

 before midsummer, and later on a fresh lot of healthy leaves grow ; 

 but in the meanwhile much damage has been done to the trees. 



Some varieties, such as the Flat China, the Elberta, and Eoyal 

 G-eorge peaches, are more subject to this disease. 



Those branches which are worse affected by the curl fungus 

 are seldom fruitful, and should be cut back and burned. The 

 mycelium hibernates in the bark, pith, and medullary rays of the 

 branches and twigs, so that it reappears each year. Massee has 

 demonstrated that the mycelium does not travel backwards from 

 the point of infection, but forwards in other words, it follows the 

 new growth. (For treatment, see table, p. 486.) 



An allied disease of the plum, called " Pocket Plums " or 

 " Bladder Plums," is caused by the fungus Exoaseus pruni, Eckl., 

 and should be treated in a like manner. 



BROWN ROT. This disease is described above. It is caused 

 by a mould or fungus, called Monilia fructigena, which attacks 

 various parts of the plant, leaves, blossoms, twigs, and fruit. 



GUMMING, SOUR SAP, OR DIE BACK. There are many diseases 

 characterised by a gummy outflow from the diseased parts or from 

 their neighbourhood. Amongst plants exhibiting this are trees like 

 the mulberry, olive, vine, fig, and vegetables like potatoes, turnips, 

 beetroot, and many others. As yet, however, no investigations 

 have been carried out carefully enough to give satisfactory 

 explanations of them. It is, however, probable (says Tubeiif) that 

 they are primarily due to errors in cultivation, while the bacteria 

 which are always found associated with them are of secondary 

 importance as disease-producers. 



G-umosis or Sour Sap, which are results rather than causes, 

 may probably be traced to an abnormal condition of the soil. 

 Sour Sap, when the roots die first, may be due to too much water ; 

 and when the tops die first, to the sudden lowering of the 

 temperature. A checked sap circulation from the stock to the 



