119 



bark. To protect the leaves from infec- 

 tion from without they should be sprayed 

 with lime-sulphur just before the flowers 

 open, and again, if necessary, immediately 

 the fruit is formed, as recommended for 

 Apple Scab. 



Apple Canker. 



A fungus, Nectria difixsima, is the 



cause of cankers often found on apple and 



pear trees (Fig. 3). It gains entrance 



through wounds and large cankers on the 



Fig. 3. 



-A Canker which lias nearly gircilec 

 an Apple Branch. 



main branches may arise in this way. On 

 neglected trees such branches are eventu- 

 ally girdled by the cankers and killed. 

 Young twigs may become infected through 

 the buds and, on some varieties of apples 

 and pears, the dying back of the young 

 branches by cankers originating through 



infection at the nodes is of frequent occur- 

 rence. During the summer the fungus is 

 to be seen on the surface of the young 

 cankers as whitish pustules bursting 

 through the bark. Each pustule produces 

 numerous spores, which, on becoming 

 detached and dispersed to other parts of 

 the tree or to other trees in the neigh- 

 bourhood, give rise to new infections. 



To keep the disease in check it is neces- 

 sary therefore to cut out and burn the 

 cankered portions as soon as they are 

 observed, for not only are they injurious 

 to the branches on which they occur, but 

 they are a source of further infection. In 

 those cases where the cankers have 

 girdled or nearly girdled the branches! 

 this operation involves cutting back to 

 below the diseased part. Where the 

 cankers have extended but a little way 

 round the branches the cankered por- 

 tions should be cut out, care being taken 

 that all discoloured wood and bark is 

 removed ; the wound should then receive 

 a coating of Stockholm tar, in order to 

 protect the exposed cut surface from fur- 

 ther infection, until it becomes naturally 

 covered over by callus. 



If the cankers are allowed to remain 

 on the trees throughout the winter the 

 fungus produces fructifications of another 

 form which are seen as minute red 

 globules in the cracks of the cankered 

 bark. The spores which develop within 

 these fructifications are set free and dis- 

 persed in the spring, thus providing for 

 fresh outbreaks of the disease. 



Brown Kot Diseases. 



Of the various forms of disease caused 

 by the Brown Rot fungi, Monilia (Selero- 

 finia) fructigena and Monilia cinerea, 

 the most familiar is a rotting of the fruit. 

 The Brown Rot of ripening apples is caused 

 by Monilia fructigena which, on gaining 

 entrance through a wound in the skin, 

 spreads rapidly through the flesh, and soon 

 appears at the surface as yellowish tufts 

 (Fig. 4), often produced in irregular con- 

 centric circles round the point of infection. 

 The tufts become powdery with innumer- 

 able minute spores which are borne in the 

 wind from the diseased fruit to others on 

 the same tree or on surrounding trees. 

 Apples in contact with diseased ones 

 become infected by contagion, and thus 



