APPLE DISEASES. 81 



Spraying the trees with dilute Bordeaux Mixture (Nos. 

 20 or 21) is a good preventive of the disease. Spray first 

 when the buds begin to open; again when the petals fall; 

 and, lastly, when the young fruit begins to form. It is 

 also advisable to spray the trees thoroughly in winter with 

 a sulphate of iron solution. (Formula 29). 



Apple Tree Canker (Nectria ditissima).— This is 

 one of the many disearses of fruit trees that, although 

 very well known, is much more injurious than is generally 

 supposed, judging from the vast number of infected trees 

 that abound almost everywhere. Apple trees are invaded 

 by the fungus in two different ways. When thick 

 branches are attacked the disease almost invariably first 

 appears in the fork of a branch, the wound that enabled 

 the fungus to enter the tissues being caused by a crack, 

 which is often formed when the branch is heavily laden 

 with foliage or fruit. Ai'tt?r infection the mycelium of the 

 fungus first attacks the baik, which often cracks in con- 

 centric ringts, and afterwards becomes ii'regularly cankered 

 or eaten aWay; at a later stage the wood is also attacked, 

 when the nutrition of the branch beyond the wound is 

 interfered with, and, as a result of starvation, the produc- 

 tion of both foliage and fruit is more or less checked. Iii 

 addition to this, the spores of the fungus are produced in 

 profusion on the cankered portion, which acts as a centre 

 or nursery for furnishing the means of extending the dis- 

 ease to neighbouring trees. The second method of infec- 

 tion takes place on one- or two-year-old branches, the 

 spores finding an entrance into the branch through punc- 

 tures made in the tender bark by insects, hailstones, etc. 

 This means of infection takes place in spite of the best 

 possible methods of cultivation. What can be effected, 

 however, by judicious pruning is to remove all surplus 

 shoots, and thus reduce the chances of infection; and even 

 after the fungus has gained a foothold the prompt removal 

 of diseased branches is imperative, as in young, tender 

 shoots the fungus acts much more vigorously than in the 



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